diff --git a/DesignPatternsSolution/Execise.Tests/UnitTests.cs b/DesignPatternsSolution/Execise.Tests/UnitTests.cs
index 0a3b80e..1aef735 100644
--- a/DesignPatternsSolution/Execise.Tests/UnitTests.cs
+++ b/DesignPatternsSolution/Execise.Tests/UnitTests.cs
@@ -12,18 +12,29 @@ 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 lib1 = Library.Instance;
+            Library lib2 = Library.Instance;
+            Assert.ReferenceEquals(lib1, lib2);
         }
 
-        //test that an book was registered successfully by checking the returned Id value is not -1
+        //test that a book was registered successfully by checking the returned Id value is not -1
         [TestMethod]
         public void BookShouldRegister()
         {
+            Library lib1 = Library.Instance;
+            Book book1 = new Book("I am Great", "Donald Trump", 2017, 19);
+            int result = lib1.Register(book1);
+            Assert.AreNotEqual(result, -1);
         }
 
-        //test that an customer was registered successfully by checking the returned Id value is not -1
+        //test that a customer was registered successfully by checking the returned Id value is not -1
         [TestMethod]
         public void CustomerShouldRegister()
         {
+            Library lib1 = Library.Instance;
+            Customer cust1 = new Customer("Daffy Duck", "123 Dippy Lane, Disneyland, CA");
+            int result = lib1.Register(cust1);
+            Assert.AreNotEqual(result, -1);
         }
 
         //test that a book can be borrowed
@@ -32,7 +43,12 @@ 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.
-            
-        }       
+            Library lib1 = Library.Instance;
+            Book book1 = new Book("I am Great", "Donald Trump", 2017, 19);
+            int result = lib1.Register(book1);
+
+            Assert.AreNotEqual(result, -1);
+
+        }
     }
 }
diff --git a/DesignPatternsSolution/Exercise/BookBorrowable.cs b/DesignPatternsSolution/Exercise/BookBorrowable.cs
index 21bd9cf..b8c7e07 100644
--- a/DesignPatternsSolution/Exercise/BookBorrowable.cs
+++ b/DesignPatternsSolution/Exercise/BookBorrowable.cs
@@ -2,6 +2,6 @@
 {
     public class BookBorrowable 
     {
-       
+        // find book in Registration Repository as class RegisteredObject and return Available Amount?
     }
 }
diff --git a/DesignPatternsSolution/Exercise/Item.cs b/DesignPatternsSolution/Exercise/Item.cs
index 92c21e1..452022b 100644
--- a/DesignPatternsSolution/Exercise/Item.cs
+++ b/DesignPatternsSolution/Exercise/Item.cs
@@ -1,6 +1,6 @@
 namespace Exercise
 {
-    public abstract class Item : LibObject
+    public abstract class Item : LibObject, IRegistarable
     {
         public Item(int amount, int year)
         {
@@ -8,15 +8,34 @@ public Item(int amount, int year)
             ObjType = ObjectType.Item;
             YearCreated = year;
         }
+
+        //public int Register()
+        //{
+        //    return 0;
+        //}
+
+        public abstract RegisteredObject GetRegistrationInfo();
+
     }
 
     public class Book : Item
     {
-        public Book(string author, string title, int year, int amount) : base(amount, year)
+        public Book(string author, string title, int year, int amount)
+            : base(amount, year)
         {
             NameOrTitle = title;
             Author = author;
         }
         public string Author { get; set; }
+
+        //my code
+        public override RegisteredObject GetRegistrationInfo()
+        {
+            return new RegisteredObject
+            {
+                Info = "Book Name: " + NameOrTitle + " , Author: " + Author + " Year: " + YearCreated,
+                AvailableAmount = AvailableAmount
+            };
+        }
     }
 }
diff --git a/DesignPatternsSolution/Exercise/Library.cs b/DesignPatternsSolution/Exercise/Library.cs
index 1d9dde4..5b3e7be 100644
--- a/DesignPatternsSolution/Exercise/Library.cs
+++ b/DesignPatternsSolution/Exercise/Library.cs
@@ -1,18 +1,32 @@
 namespace Exercise
 {
-    public class Library
+    public sealed class Library
     {
         //implement Singleton to make sure only one library will exist
+        private static Library instance;
+        private Library() { }
 
-        
 
+        public static Library Instance
+        {
+            get
+            {
+                if (instance == null)
+                {
+                    instance = new Library();
+                }
+                return instance;
+            }
+        }
+
+        //public static Library getInstance() ()
         //Implement Register method by utilizing RegistrationRepository (complete missing parts)
-        public int Register()
+        public int Register(IRegistarable newRegObject)
         {
-            // return RegistrationRepository.Register();
+            return RegistrationRepository.Register(newRegObject);
 
             //dummy, just to compile
-            return 0;
+            //return 0;
         }
     }
 }
diff --git a/DesignPatternsSolution/Exercise/Person.cs b/DesignPatternsSolution/Exercise/Person.cs
index 2c2ed21..fed86e7 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, IRegistarable
     {
         public string Address { get; set; }
         public DateTime RegisteredAt { get; set; }
@@ -19,5 +19,14 @@ public void SetId(int id)
         {
             ObjectId = id;
         }
+
+        public RegisteredObject GetRegistrationInfo()
+        {
+            return new RegisteredObject
+            {
+                Info = "Customer Name: " + NameOrTitle + " , Address: " + Address + " Date Registered: " + RegisteredAt,
+                AvailableAmount = AvailableAmount
+            };
+        }
     }
 }