Given a calculator form with the HTML code and the C# code to add two numbers. Please answer below questions after the given code.

Answer both questions (a) and (b) below: Considering grade letter calculator to determine the letter grade based on numerical mark. (a) Fill in the blanks | 8 blanks) in the C# code below. (4 marks-0.5 marks each blank) double mark = Convert. -----B1---- (lblResultatext); string letterGrade "; = if (mark > 85) { letterGrade "High Distinction"; } else if (mark > 75) { ---- B2----= "Distinction"; } else if (---B3--- > 60) { letterGrade = "Credit"; } else B4---- (mark > 50) { letterGrade } B6- { letterGrade "Fail"; } Label1. ---B7--- = ---B8-; B5---- PER (b) What is the purpose of using C# decision making statements (if/else) (1 mark)? Give an example of using if-else statement (1 mark)