Researchers can verify that weights were obtained through actual measurements instead of simply asking subjects to report their weights by analyzing the last digit of each weight. People tend to round down to numbers end in 0 or 5, whereas examination procedures are exact, with numbers ending in 0, 1, ..., 9. Suppose you are given the last digits of the weights obtained from 80 randomly selected students, and you need to test the claim that the last digits of the weights do not follow a uniform distribution (all of the digits are equally likely). What is the expected frequency for the digit 7