diff --git a/DesignPatternsSolution/Execise.Tests/Execise.Tests.csproj b/DesignPatternsSolution/Execise.Tests/Execise.Tests.csproj
index 71e68ac..4f78f0d 100644
--- a/DesignPatternsSolution/Execise.Tests/Execise.Tests.csproj
+++ b/DesignPatternsSolution/Execise.Tests/Execise.Tests.csproj
@@ -8,7 +8,7 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>Execise.Tests</RootNamespace>
     <AssemblyName>Execise.Tests</AssemblyName>
-    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <ProjectTypeGuids>{3AC096D0-A1C2-E12C-1390-A8335801FDAB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">10.0</VisualStudioVersion>
@@ -16,6 +16,7 @@
     <ReferencePath>$(ProgramFiles)\Common Files\microsoft shared\VSTT\$(VisualStudioVersion)\UITestExtensionPackages</ReferencePath>
     <IsCodedUITest>False</IsCodedUITest>
     <TestProjectType>UnitTest</TestProjectType>
+    <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
diff --git a/DesignPatternsSolution/Execise.Tests/UnitTests.cs b/DesignPatternsSolution/Execise.Tests/UnitTests.cs
index 0a3b80e..cc1f627 100644
--- a/DesignPatternsSolution/Execise.Tests/UnitTests.cs
+++ b/DesignPatternsSolution/Execise.Tests/UnitTests.cs
@@ -12,24 +12,38 @@ 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
+            var firstInstanceLibrary = Library.getLibrary();
+            var secondInstanceLibrary = Library.getLibrary();
+
+            Assert.AreSame(firstInstanceLibrary, secondInstanceLibrary);
+
         }
 
         //test that an book was registered successfully by checking the returned Id value is not -1
         [TestMethod]
         public void BookShouldRegister()
         {
+            var library = Library.getLibrary();
+            var value = library.Register(new Book("Bob", "The Book", 1922, 10));
+            Assert.AreNotEqual(-1, value);
         }
 
         //test that an customer was registered successfully by checking the returned Id value is not -1
         [TestMethod]
         public void CustomerShouldRegister()
         {
+            var library = Library.getLibrary();
+            var value = library.Register(new Customer("bob", "200 street"));
+            Assert.AreNotEqual(-1, value);
         }
 
         //test that a book can be borrowed
         [TestMethod]
         public void CanBorrowBook()
         {
+            var books = new BookBorrowable("bob", "The book", 1822, 8);
+            books.BorrowOne();
+            Assert.AreEqual(7, books.getAvailableAmount());
             //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.
             
diff --git a/DesignPatternsSolution/Exercise/BookBorrowable.cs b/DesignPatternsSolution/Exercise/BookBorrowable.cs
index 21bd9cf..d68d276 100644
--- a/DesignPatternsSolution/Exercise/BookBorrowable.cs
+++ b/DesignPatternsSolution/Exercise/BookBorrowable.cs
@@ -1,7 +1,20 @@
 namespace Exercise
 {
-    public class BookBorrowable 
+    public class BookBorrowable: Book
     {
-       
+        public BookBorrowable(string author, string title, int year, int amount): base(author, title, year, amount)
+        {
+
+        }      
+
+        public void BorrowOne() {
+            this.AvailableAmount--;
+        }
+
+        public int getAvailableAmount()
+        {
+            return this.AvailableAmount;
+        }
     }
+
 }
diff --git a/DesignPatternsSolution/Exercise/Exercise.csproj b/DesignPatternsSolution/Exercise/Exercise.csproj
index d2cc582..87a49ae 100644
--- a/DesignPatternsSolution/Exercise/Exercise.csproj
+++ b/DesignPatternsSolution/Exercise/Exercise.csproj
@@ -9,9 +9,10 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>Exercise</RootNamespace>
     <AssemblyName>Exercise</AssemblyName>
-    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
+    <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
diff --git a/DesignPatternsSolution/Exercise/Item.cs b/DesignPatternsSolution/Exercise/Item.cs
index 92c21e1..5c3dee5 100644
--- a/DesignPatternsSolution/Exercise/Item.cs
+++ b/DesignPatternsSolution/Exercise/Item.cs
@@ -10,13 +10,23 @@ public Item(int amount, int year)
         }
     }
 
-    public class Book : Item
+    public class Book : Item, IRegistarable
     {
+        private RegisteredObject registeredObject;
+
         public Book(string author, string title, int year, int amount) : base(amount, year)
         {
             NameOrTitle = title;
             Author = author;
+            registeredObject = new RegisteredObject();
+            registeredObject.Info = "Book";
+            registeredObject.AvailableAmount = amount;
         }
         public string Author { get; set; }
+
+        public RegisteredObject GetRegistrationInfo()
+        {
+            return registeredObject;
+        }
     }
 }
diff --git a/DesignPatternsSolution/Exercise/Library.cs b/DesignPatternsSolution/Exercise/Library.cs
index 1d9dde4..38c6fac 100644
--- a/DesignPatternsSolution/Exercise/Library.cs
+++ b/DesignPatternsSolution/Exercise/Library.cs
@@ -3,16 +3,18 @@
     public class Library
     {
         //implement Singleton to make sure only one library will exist
+        static Library library = new Library();
 
+
+        private Library() { }
+
+        public static Library getLibrary() { return library; }
         
 
         //Implement Register method by utilizing RegistrationRepository (complete missing parts)
-        public int Register()
+        public int Register(IRegistarable register)
         {
-            // return RegistrationRepository.Register();
-
-            //dummy, just to compile
-            return 0;
+            return RegistrationRepository.Register(register);
         }
     }
 }
diff --git a/DesignPatternsSolution/Exercise/Person.cs b/DesignPatternsSolution/Exercise/Person.cs
index 2c2ed21..addf5c1 100644
--- a/DesignPatternsSolution/Exercise/Person.cs
+++ b/DesignPatternsSolution/Exercise/Person.cs
@@ -2,10 +2,11 @@
 
 namespace Exercise
 {
-    public class Customer : LibObject
+    public class Customer : LibObject, IRegistarable
     {
         public string Address { get; set; }
         public DateTime RegisteredAt { get; set; }
+        private RegisteredObject registeredObject;
 
         public Customer(string name, string addr)
         {
@@ -13,11 +14,19 @@ public Customer(string name, string addr)
             Address = addr;
             RegisteredAt = DateTime.Now;
             ObjType = ObjectType.Person;
+            registeredObject = new RegisteredObject();
+            registeredObject.Info = "information";
         }
 
         public void SetId(int id)
         {
             ObjectId = id;
         }
+
+        public RegisteredObject GetRegistrationInfo()
+        {
+            return registeredObject;
+        }
+
     }
 }