diff --git a/DesignPatternsSolution/DesignPatternsSolution.sln b/DesignPatternsSolution/DesignPatternsSolution.sln
index e5b257d..83033f8 100644
--- a/DesignPatternsSolution/DesignPatternsSolution.sln
+++ b/DesignPatternsSolution/DesignPatternsSolution.sln
@@ -1,11 +1,11 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 14
-VisualStudioVersion = 14.0.24720.0
+# Visual Studio 2013
+VisualStudioVersion = 12.0.31101.0
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Exercise", "Exercise\Exercise.csproj", "{EA98A53A-F8CD-4539-9E57-1FEF2D64F13A}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Execise.Tests", "Execise.Tests\Execise.Tests.csproj", "{464FBD03-CA8B-4926-8F69-66726819DA02}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Exercise.Tests", "Execise.Tests\Exercise.Tests.csproj", "{464FBD03-CA8B-4926-8F69-66726819DA02}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Documents", "Documents", "{8C88EFFA-EC68-42ED-A482-A7B8964538E8}"
 	ProjectSection(SolutionItems) = preProject
diff --git a/DesignPatternsSolution/Execise.Tests/Execise.Tests.csproj b/DesignPatternsSolution/Execise.Tests/Exercise.Tests.csproj
similarity index 98%
rename from DesignPatternsSolution/Execise.Tests/Execise.Tests.csproj
rename to DesignPatternsSolution/Execise.Tests/Exercise.Tests.csproj
index 317ab1f..ea9919a 100644
--- a/DesignPatternsSolution/Execise.Tests/Execise.Tests.csproj
+++ b/DesignPatternsSolution/Execise.Tests/Exercise.Tests.csproj
@@ -6,7 +6,7 @@
     <ProjectGuid>{464FBD03-CA8B-4926-8F69-66726819DA02}</ProjectGuid>
     <OutputType>Library</OutputType>
     <AppDesignerFolder>Properties</AppDesignerFolder>
-    <RootNamespace>Execise.Tests</RootNamespace>
+    <RootNamespace>Exercise.Tests</RootNamespace>
     <AssemblyName>Execise.Tests</AssemblyName>
     <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
diff --git a/DesignPatternsSolution/Execise.Tests/Properties/AssemblyInfo.cs b/DesignPatternsSolution/Execise.Tests/Properties/AssemblyInfo.cs
index b8d1030..cc8baf1 100644
--- a/DesignPatternsSolution/Execise.Tests/Properties/AssemblyInfo.cs
+++ b/DesignPatternsSolution/Execise.Tests/Properties/AssemblyInfo.cs
@@ -5,11 +5,11 @@
 // General Information about an assembly is controlled through the following 
 // set of attributes. Change these attribute values to modify the information
 // associated with an assembly.
-[assembly: AssemblyTitle("Execise.Tests")]
+[assembly: AssemblyTitle("Exercise.Tests")]
 [assembly: AssemblyDescription("")]
 [assembly: AssemblyConfiguration("")]
 [assembly: AssemblyCompany("")]
-[assembly: AssemblyProduct("Execise.Tests")]
+[assembly: AssemblyProduct("Exercise.Tests")]
 [assembly: AssemblyCopyright("Copyright ©  2016")]
 [assembly: AssemblyTrademark("")]
 [assembly: AssemblyCulture("")]
diff --git a/DesignPatternsSolution/Execise.Tests/UnitTests.cs b/DesignPatternsSolution/Execise.Tests/UnitTests.cs
index 0a3b80e..1bab1db 100644
--- a/DesignPatternsSolution/Execise.Tests/UnitTests.cs
+++ b/DesignPatternsSolution/Execise.Tests/UnitTests.cs
@@ -1,7 +1,7 @@
 using Exercise;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
-namespace Execise.Tests
+namespace Exercise.Tests
 {
     [TestClass]
     public class UnitTests
@@ -10,29 +10,44 @@ public class UnitTests
         [TestMethod]
         public void LibraryShouldBeSingleton()
         {
-            //check that when you create a Library instance second time, 
-            //you get exactly the same instance as for a very first time
+            Library libraryInstance1 = Library.GetInstance();
+            Library libraryInstance2 = Library.GetInstance();
+
+            Assert.AreEqual(libraryInstance1, libraryInstance2);
         }
 
         //test that an book was registered successfully by checking the returned Id value is not -1
         [TestMethod]
         public void BookShouldRegister()
         {
+            Book book = new Book("Cash Craig", "Fake Book", 1991, 7);
+            int result = RegistrationRepository.Register(book);
+            Assert.AreNotEqual(-1, result);
         }
 
         //test that an customer was registered successfully by checking the returned Id value is not -1
         [TestMethod]
         public void CustomerShouldRegister()
         {
+            Customer customer = new Customer("Cash Craig", "123 Fake Street");
+            int result = RegistrationRepository.Register(customer);
+            Assert.AreNotEqual(-1, result);
         }
 
         //test that a book can be borrowed
         [TestMethod]
         public void CanBorrowBook()
         {
-            //create a borrowable book with available amount more than one. 
-            //Run BorrowOne method of the BookBorrowable instance. Check that total amount was reduced by one.
-            
+            Book myBook = new Book("Cash Craig", "Fake Book", 1991, 7);
+
+            int oldCount = myBook.AvailableAmount;
+
+            Borrowable bookBorrowable = new Borrowable(null, new Borrow(myBook));
+            bookBorrowable.BorrowOne();
+
+            int newCount = myBook.AvailableAmount;
+
+            Assert.AreEqual(oldCount - 1, newCount);
         }       
     }
 }
diff --git a/DesignPatternsSolution/Exercise/BookBorrowable.cs b/DesignPatternsSolution/Exercise/BookBorrowable.cs
index 21bd9cf..412c90f 100644
--- a/DesignPatternsSolution/Exercise/BookBorrowable.cs
+++ b/DesignPatternsSolution/Exercise/BookBorrowable.cs
@@ -1,7 +1,48 @@
 namespace Exercise
 {
-    public class BookBorrowable 
+    public abstract class ABorrowable 
     {
-       
+        public virtual void BorrowOne() { }
+        protected Borrow Borrow;
+
+        protected ABorrowable(Borrow borrow)
+        {
+            this.Borrow = borrow;
+        }
+    }
+
+    public class Borrowable : ABorrowable
+    {
+        private readonly ABorrowable _borrowable;
+
+        public Borrowable(ABorrowable borrowable, Borrow borrow) : base(borrow)
+        {
+            _borrowable = borrowable;
+        }
+
+        public override void BorrowOne()
+        {
+            if (_borrowable != null)
+            {
+                _borrowable.BorrowOne();
+            }
+
+            Borrow.BorrowOne();
+        }
+    }
+
+    public class Borrow
+    {
+        private readonly LibObject _libObject;
+
+        public Borrow(LibObject libObject)
+        {
+            this._libObject = libObject;
+        }
+
+        public void BorrowOne()
+        {
+            this._libObject.AvailableAmount--;
+        }
     }
 }
diff --git a/DesignPatternsSolution/Exercise/Item.cs b/DesignPatternsSolution/Exercise/Item.cs
index 92c21e1..2184cde 100644
--- a/DesignPatternsSolution/Exercise/Item.cs
+++ b/DesignPatternsSolution/Exercise/Item.cs
@@ -2,7 +2,7 @@
 {
     public abstract class Item : LibObject
     {
-        public Item(int amount, int year)
+        protected Item(int amount, int year)
         {
             AvailableAmount = amount;
             ObjType = ObjectType.Item;
@@ -10,7 +10,7 @@ public Item(int amount, int year)
         }
     }
 
-    public class Book : Item
+    public class Book : Item, IRegistrable
     {
         public Book(string author, string title, int year, int amount) : base(amount, year)
         {
@@ -18,5 +18,14 @@ public Book(string author, string title, int year, int amount) : base(amount, ye
             Author = author;
         }
         public string Author { get; set; }
+
+        public RegisteredObject GetRegistrationInfo()
+        {
+            RegisteredObject resgisteredObject = new RegisteredObject();
+            resgisteredObject.Info = this.NameOrTitle;
+            resgisteredObject.AvailableAmount = this.AvailableAmount;
+
+            return resgisteredObject;
+        }
     }
 }
diff --git a/DesignPatternsSolution/Exercise/Library.cs b/DesignPatternsSolution/Exercise/Library.cs
index 1d9dde4..dc84b01 100644
--- a/DesignPatternsSolution/Exercise/Library.cs
+++ b/DesignPatternsSolution/Exercise/Library.cs
@@ -2,16 +2,19 @@
 {
     public class Library
     {
-        //implement Singleton to make sure only one library will exist
+        private static readonly Library Instance = new Library();
 
-        
+        private Library()
+        {
+        }
 
-        //Implement Register method by utilizing RegistrationRepository (complete missing parts)
-        public int Register()
+        public static Library GetInstance()
         {
-            // return RegistrationRepository.Register();
+            return Instance;
+        }
 
-            //dummy, just to compile
+        public int Register()
+        {
             return 0;
         }
     }
diff --git a/DesignPatternsSolution/Exercise/Person.cs b/DesignPatternsSolution/Exercise/Person.cs
index 2c2ed21..06e2cad 100644
--- a/DesignPatternsSolution/Exercise/Person.cs
+++ b/DesignPatternsSolution/Exercise/Person.cs
@@ -2,7 +2,7 @@
 
 namespace Exercise
 {
-    public class Customer : LibObject
+    public class Customer : LibObject, IRegistrable
     {
         public string Address { get; set; }
         public DateTime RegisteredAt { get; set; }
@@ -19,5 +19,14 @@ public void SetId(int id)
         {
             ObjectId = id;
         }
+
+        public RegisteredObject GetRegistrationInfo()
+        {
+            RegisteredObject registeredObject = new RegisteredObject();
+            registeredObject.Info = this.NameOrTitle;
+            registeredObject.AvailableAmount = this.AvailableAmount;
+            
+            return registeredObject;
+        }
     }
 }
diff --git a/DesignPatternsSolution/Exercise/Registration.cs b/DesignPatternsSolution/Exercise/Registration.cs
index f8c4eb0..d21240e 100644
--- a/DesignPatternsSolution/Exercise/Registration.cs
+++ b/DesignPatternsSolution/Exercise/Registration.cs
@@ -3,42 +3,35 @@
 using System.Linq;
 namespace Exercise
 {
-    public interface IRegistarable
+    public interface IRegistrable
     {
         RegisteredObject GetRegistrationInfo();
     }
 
     public static class RegistrationRepository
     {
-        //registered objects list
-        private static List<RegisteredObject> _registeredList = new List<RegisteredObject>();
+        private static readonly List<RegisteredObject> RegisteredList = new List<RegisteredObject>();
 
         private static int _nextId = 1;
 
-        //With BRIDGE pattern, implement Register method so it will accept both a Person and an Item
-        public static int Register(IRegistarable registarable)
+        public static int Register(IRegistrable registrable)
         {
-            //get info from an lib object
-            var info = registarable.GetRegistrationInfo();
+            var info = registrable.GetRegistrationInfo();
             if (info == null) return -1;
 
-            //get new id for for the registered object
             info.Id = _nextId;
 
-            //add to registration repository
-            _registeredList.Add(info);
+            RegisteredList.Add(info); 
 
-            //store next available id
-            _nextId = _registeredList.Count + 1;
+            _nextId = RegisteredList.Count + 1;
 
-            //return success
             return info.Id;
         }
 
         public static int DeleteAllRegisteredItems()
         {
-            var size = _registeredList.Count();
-            _registeredList.RemoveRange(0, size);
+            var size = RegisteredList.Count();
+            RegisteredList.RemoveRange(0, size);
             _nextId = 1;
 
             return size;