5.34 Taste Test for PTC The taste test for PTC (phenylthiocarbamide) is a favourite exercise for every human genetics class. It has been established that a single gene determines the characteristic, and that 70% of Canadians are "tasters," while 30% are "non-tasters." Suppose that 20 Canadians are randomly chosen and are tested for PTC.

a. What is the probability that 17 or more are "tasters"?

b. What is the probability that 15 or fewer are "tasters"?