In early 2012, it was reported that 38% of U.S. adult cell phone owners called a friend

Question:

In early 2012, it was reported that 38% of U.S. adult cell phone owners called a friend for advice about a purchase while in a store. (Data extracted from "Mobile Advice, Sunday Stats" The Palm Beach Post, February 19, 2012, p. IF,) If a sample of 10 U.S. adult cell phone owners is selected, what is the probability that
a. 6 called a friend for advice about a purchase while in a store?
b. at least 6 called a friend for advice about a purchase while in a store?
c. all 10 called a friend for advice about a purchase while in a store?
d. If you selected the sample in a particular geographical area and found that none of the 10 respondents called a friend for advice about a purchase while in a store, what conclusion might you reach about whether the percentage of adult cell phone owners who called a friend for advice about a purchase while in a store in this area was 38%?