Question: An appliance store sells 20 refrigerators each week. Ten percent of all purchasers of a refrigerator buy an extended warranty. Let X denote the number of the next 20 purchasers who do so.
a. Verify that X satisfies the conditions for a binomial random variable, and find n and p.
b. Find the probability that X is zero.
c. Find the probability that X is two, three, or four.
d. Find the probability that X is at least five.