I need to code a grading system that creates a list using values from a dictionary and sorts them based off their integer value, assigning each value to a letter grade. The format looks like this:

A: (value)

B: (value)

C: (value)

D: (value)

F: (value)

Assume each letter grade is by values of 10, so 90-100 = A, 80-90 = B, and so on