The quality control manager of a restaurant wants to analyze the length of time a car spends at the drive-through window waiting for an order. It is determined that the mean time spent at the window is 59.3 seconds with a standard deviation of 13.1 seconds. The distribution of time at the window is skewed right.

(a) To obtain probabilities regarding a sample mean using the normal model, what size sample is required?

(b) What is the probability of obtaining a sample mean of 56.8 seconds or less, assuming that the population mean is 59.3 seconds?

(c) Do you think that the new system is effective? Why or Why not?