diff --git a/CourseApp.Tests/InterfaceTests.cs b/CourseApp.Tests/InterfaceTests.cs
new file mode 100644
index 00000000..3445f4f8
--- /dev/null
+++ b/CourseApp.Tests/InterfaceTests.cs
@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using Xunit;
+
+namespace CourseApp.Tests
+{
+    public class InterfaceTests
+    {
+        [Fact]
+        public void Test1()
+        {
+            Assert.True(true);
+        }
+
+        [Fact]
+        public void IComparable()
+        {
+            Animal[] mass = new Animal[3];
+            mass[0] = new Cat("Name1", 6, true, true);
+            mass[1] = new Mouse("Name2", 1, false, true);
+            mass[2] = new Cat("Name3", 3, false, true);
+            Array.Sort(mass);
+            Assert.Equal("Name2", mass[0].Name);
+            Assert.Equal("Name3", mass[1].Name);
+            Assert.Equal("Name1", mass[2].Name);
+        }
+    }
+}
\ No newline at end of file
diff --git a/CourseApp/Animal.cs b/CourseApp/Animal.cs
index f859af6f..617d313c 100644
--- a/CourseApp/Animal.cs
+++ b/CourseApp/Animal.cs
@@ -2,7 +2,7 @@
 
 namespace CourseApp
 {
-    public abstract class Animal
+    public abstract class Animal : IComparable<Animal>
     {
         private int age;
 
@@ -51,5 +51,10 @@ public override string ToString()
         }
 
         public abstract string Voice();
+
+        public int CompareTo(Animal an)
+        {
+            return this.Age.CompareTo(an.Age);
+        }
     }
 }
\ No newline at end of file
diff --git a/CourseApp/Cat.cs b/CourseApp/Cat.cs
index 6daf2a93..0c034d93 100644
--- a/CourseApp/Cat.cs
+++ b/CourseApp/Cat.cs
@@ -4,7 +4,7 @@
 
 namespace CourseApp
 {
-    public class Cat : Animal
+    public class Cat : Animal, IFacts
     {
         public Cat()
         : this("Неизвестно")
@@ -58,5 +58,7 @@ public override string Voice()
         {
             return "Meow";
         }
+
+        void IFacts.Facts() => Console.WriteLine("Сердце кошки бьется около 140 ударов в минуту.\nМяуканьем кошки пытаются обратить внимание человека.\n Усы, необходимы кошке для перемещения в пространстве.");
     }
-}
\ No newline at end of file
+}
diff --git a/CourseApp/IFacts.cs b/CourseApp/IFacts.cs
new file mode 100644
index 00000000..3354caf9
--- /dev/null
+++ b/CourseApp/IFacts.cs
@@ -0,0 +1,7 @@
+namespace CourseApp
+{
+    public interface IFacts
+    {
+        void Facts();
+    }
+}
\ No newline at end of file
diff --git a/CourseApp/Program.cs b/CourseApp/Program.cs
index afa38911..e5f9819e 100644
--- a/CourseApp/Program.cs
+++ b/CourseApp/Program.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 
 namespace CourseApp
@@ -7,8 +7,8 @@ public class Program
     {
         public static double MyFunction(double a, double x)
         {
-             var y = Math.Pow(Math.Log10(a + x), 2) / Math.Pow(a + x, 2);
-             return y;
+            var y = Math.Pow(Math.Log10(a + x), 2) / Math.Pow(a + x, 2);
+            return y;
         }
 
         public static List<double> TaskA(double a, double xn, double xk, double dx)
@@ -62,9 +62,10 @@ public static void Main(string[] args)
 
             Console.WriteLine();
 
-            Animal[] masss = new Animal[2];
-            masss[0] = new Mouse("Larisa", 2, false, true);
-            masss[1] = new Cat("Kyza", 7, true, true);
+            Animal[] masss = new Animal[3];
+            masss[0] = new Cat("Kyza", 7, true, true);
+            masss[1] = new Mouse("Larisa", 2, false, true);
+            masss[2] = new Cat("Murzik", 4, true, false);
             foreach (var item in masss)
             {
                 Console.WriteLine(item.ToString());
@@ -72,6 +73,17 @@ public static void Main(string[] args)
                 Console.WriteLine();
             }
 
+            Array.Sort(masss);
+            Console.WriteLine("Отсортированный по возрасту массив:");
+            foreach (Animal an in masss)
+            {
+                Console.WriteLine($"{an.Name} - {an.Age}");
+            }
+
+            Console.WriteLine("================================");
+
+            IFacts barsik = new Cat("Barsik", 5, true, true);
+            barsik.Facts();
             Console.ReadLine();
         }
     }