The time required for an automotive center to complete an oil change service an automobile approximately falls in normal distribution, with a mean of 17 minutes and a standard deviation of 3.5 minutes.

(a) The automotive center guarantees customers that the service will take no longer than 20 minutes. If it does take longer, the customer will receive their service for half price. What percentage of customers receive the service for half price?

(b) if the automotive center does not want to get the discount more than 2% of its customers, how long should it make the guaranteed time limit?

(a) The person the customers I received the cities for half price is ____% (round to two decimal places as needed)

(b) The guaranteed time limit____minutes (round up to the nearest minute)