### Ranges of grade for variation and quantity

1) a student must have an average (the mean) on five tests that is greater than or equal to 80% but less than 90% to receive a final grade of B. Devons grades on the first four tests were 76%,63%,91%, and 80%. What range of grades on the fifth test would give him a B in the course? (assume that 100% is the highest possible grade