The average life of a Rolling Rock tire is normally distributed with a mean of 40,000 miles and a standard deviation of 5,000 miles. Think about the four probabilities that follow. You do not have to calculate these probabilities. Instead, simply rank these four probabilities from largest to smallest; for example, if you think that

(a) has the highest probability,

(b) the next highest,

(c) the next highest, and

(d) the smallest probability, your answer would be

a, b,

c, d.

a. A tire will last more than 40,000 miles.

b. A tire will last more than 50,000 miles.

c. The average life of a random sample of four tires will be more than 40,000 miles.

d. The average life of a random sample of four tires will be more than 50,000 miles.