A sample of 100 students is to be taken to determine which of two brands of beer

Question:

A sample of 100 students is to be taken to determine which of two brands of beer is preferred in a blind taste test. Suppose that, in the whole population of students, 50% would prefer brand A.
a. What is the probability that more than 60% of the sample members prefer brand A?
b. What is the probability that between 45% and 55% of the sample members prefer brand A?