6. Fast Auto Service provides oil and lube service for cars. It is known that the mean time taken for oil and lube service at this garage is 15 minutes with a standard deviation of 2.4 minutes. The manager wants to promote the business by guaranteeing a maximum waiting time for its customers. If a customer's car is not finished within this time, they will get a 50% discount. The manager wants to limit this discount to at most 5% of its customers. What should the guaranteed maximum waiting time be set at? (Hint: This problem starts off by giving you the percentage under the curve. You need to find the corresponding standard score, and then convert it to a time in minutes using the relationship st score = observation - mean -.) Also provide a drawing of the normal curve st.dev. with the appropriate area shaded and the guaranteed maximum waiting time indicated