Write a C# .NET Windows Forms application, with all the functionality implemented. [10 marks] a) Build the GUI as shown below. [4 marks] b) Sum will add all the values [3 marks] c) Average will average all the values [3 marks] d) No marks for implementing Input, Clear, Remove buttons as these are already implemented in the code example covered during the class. Grade Book Form 10 20 30 40 50 70 Input Clear Remove Sum X Grade Book Form 10 20 30 40 50 60 Input Clear Remove Sum