Added undo function

GPA Calculator/Program.cs

@@ -14,11 +14,19 @@ namespace GPA_Calculator
             {
                 RenderGrades();
                 inputGrade = Console.ReadLine();
-                inputGrade = inputGrade.Replace("+", "Plus").Replace("-", "Minus");
+                inputGrade = inputGrade.ToUpper().Replace("+", "Plus").Replace("-", "Minus");
                 if(Enum.TryParse<Grade>(inputGrade, out Grade grade))
                 {
                     GradesList.Add(grade);
                 }
+                else if (inputGrade == "clear")
+                {
+                    GradesList = new List<Grade>();
+                }
+                else if (inputGrade == "undo" && GradesList.Count > 0)
+                {
+                    GradesList.RemoveAt(GradesList.Count - 1);
+                }
             }
         }
 
@@ -38,7 +46,7 @@ namespace GPA_Calculator
             {
                 Console.SetCursorPosition(0, 3);
                 Console.WriteLine("GPA: ");
-                Console.WriteLine(totalGrade / GradesList.Count);
+                Console.WriteLine((totalGrade / GradesList.Count).ToString("0.##"));
             }
 
             Console.SetCursorPosition(0, 1);