7.111 Suppose that fuel efficiency for a particular model car under specified conditions is normally distributed with a mean value of 30.0 mpg and a standard deviation of 1.2 mpg.

a. What is the probability that the fuel efficiency for a randomly selected car of this type is between 29 and 31 mpg?

b. Would it surprise you to find that the efficiency of a randomly selected car of this model is less than 25 mpg?

c. If three cars of this model are randomly selected, what is the probability that all three have efficiencies exceeding 32 mpg?

d. Find a number c* such that 95% of all cars of this model have efficiencies exceeding c* (i.e., P(x . c*) 5 .95).