A Used Car Salesman in a Small Town States That

Short Answer

A used car salesman in a small town states that, on the average, it takes him 5 days to sell a car. Assume that the probability distribution of the length of time between sales is exponentially distributed.
a. What is the probability that he will have to wait at least 8 days before making another sale?
b. What is the probability that he will have to wait between 6 and 10 days before making another sale?