The time required for an automotive center to finish an oil change service on an automobile approximately follows a normaldistribution, with a mean of 17 minutes and a standard deviation of 2.5 minutes.

a) The automotive center guarantees customers that the service will take no longer than 20 minutes. If it does takelonger, the customer will receive the service forhalf-price. What percent of customers receive the service forhalf-price?

b) If the automotive center does not want to give the discount more than 2% of itscustomers, how long should it make the guaranteed timelimit