The time to failure of a certain make of automobile transmis

The time to failure of a certain make of automobile transmissions is known to follow the exponential distribution, with a mean of 100,000 miles. . If these transmissions carry a warranty for 75,000 miles, then:
a. What proportion of the transmissions will need repair before the warranty expires?
b. If no more than 4% of the population can be replaced economically under warranty, what warranty time would be economically feasible?

Solution