Between 5:00 _PM and 6:00 PM, cars arrive at Jiffy Lube at the rate of 9 cars per hour (0.15 car per minute).The following formula from statistics can be used to determine the probability that a car will arrive within t minutes of 5:00 _PM.

F(t) = 1 – e-^0.15t

(a) Determine how many minutes are needed for the probability to reach 50%.
(b) Determine how many minutes are needed for the probability to reach 80%.