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- (lblResult.Text); string letterscade if (mark > 85) { letterGrade - "High Distinction"; } else if (mark > 75) { B2-= "Distinction"; } else if (---B3- > 60) { letterGrade "Credit"; } else -B4-- (mark > 50) { letterGcade -B5- } B6- { letterGrade - "Fail"; } Label1. -B7- B8-; (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)