Created Book.cs for class creation

gradebook/src/GradeBook/Book.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+
+namespace GradeBook
+{
+    class Book
+    {
+        private List<double> grades;
+        private string name;
+
+        public Book(string name)
+        {
+            this.name = name;
+            grades = new List<double>();
+        }
+
+        public void AddGrade(double grade)
+        {
+            this.grades.Add(grade);
+        }
+    }
+    
+}

gradebook/src/GradeBook/Program.cs

@@ -7,24 +7,29 @@ namespace GradeBook
     {
         static void Main(string[] args)
         {
+
+            var book = new Book("Scott's Grade Book");
+            book.AddGrade(89.1);
+            book.AddGrade(90.5);
+
             List<double> grades = new List<double>() {12.7, 10.3, 6.11, 4.1};
             grades.Add(56.1);
             double result = 0;
+            var highGrade = double.MinValue;
+            var lowGrade = double.MaxValue;
 
             foreach (var number in grades)
             {
+                highGrade = Math.Max(number, highGrade);
+                lowGrade = Math.Min(number, lowGrade);
+                
                 result += number;
             }
             result /= grades.Count;
 
-            System.Console.WriteLine($"The average grade is {result}");
-
-            if (args.Length > 0)
-            {
-                Console.WriteLine($"Hello, {args[0]}!");
-            } else{
-                Console.WriteLine("Where is the name?");
-            }
+            Console.WriteLine($"The average grade is {result:N1}");
+            Console.WriteLine($"The highest grade is {highGrade:N1}");
+            Console.WriteLine($"The lowest grade is {lowGrade:N1}");
         }
     }
 }