Complete the program below so that it prompts for and reads in a student's final class average (0.0 to 100.0), and prints out the letter grade the student should receive, based on the following table:

• A : greater than 90.0, up to 100.0
• B : greater than 80.0, up to 90.0
• C : greater than 70.0, up to 80.0
• D : greater than 60.0, up to 70.0
• F : 0.0 up to 60.0

For example, if a student's final class average is 84.6, he has earned a letter grade of B.