C# language

Prompt the user to enter a sequence of non-negative numbers that ends whenever the user enters a negative number. Have a method find the mean value for the sequence that was entered. Display that value for the user.

Use a for-loop to display all odd numbers between 42 and 20 in that order.

Use a while-loop to display all even numbers between 42 and 20 in that order.

Use a do-loop to display all even numbers between 20 and 42 in that order.

Prompt the user to enter a test score between 0 and 100. Have a method use a compound if statement to convert that score into a letter grade based on the following table:

91 to 100	A
81 to 90	B
71 to 80	C
61 to 70	D
60 and below	F

Display the result for the user. NOTE: Only use 1 "return" statement in your method.

Just like with #9 above, have the user enter a numeric grade and covert it into a letter grade using a switch statement instead of a compound if statement.