Write assert statements below to test a function with the following specification. Your asserts should check that the function produces an appropriate value for each of the three postcondition cases.

def grade(score): """Determines letter grade given a numeric score Precondition: 0 <= `score` <= 100 Postcondition: Returns 'A' if 90 <= `score` <= 100, 'B' if 80 <= `score` < 90, 'F' if 0 <= `score` < 80 """