The time required for an automotive center to complete an oil change service on an automobile approximately follows a normal distribution, with a mean of 17minutes and a standard deviation of 3minutes.

(a) The automotive center guarantees customers that the service will take no longer than

20minutes. If it does take longer, the customer will receive the service for half-price. What percent of customers receive the service for half-price?

(b) If the automotive center does not want to give the discount to more than

2% of its customers, how long should it make the guaranteed time limit?

(a) The percent of customers that receive the service for half-price is

nothing %.