I (Assign grades) Write a program that reads a list of scores and then assigns grades based on the following scheme: The grade is A if score is >= best – 10. The grade is B if score is >= best - 20....

This problem is in python (image of question attached) I can't figure out how to find the highest score to assign to best. I keep getting the error "AttributeError: 'set' object has no attribute 'sort'.
My code (which isn't working) is attached as well.

Extracted text: I (Assign grades) Write a program that reads a list of scores and then assigns grades based on the following scheme: The grade is A if score is >= best – 10. The grade is B if score is >= best - 20. The grade is C if score is >= best – 30. The grade is D if score is >= best - 40. The grade is F otherwise. Here is a sample run:


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