A restaurant offers pizza delivery service to a campus dormitory. Delivery times follow a

normal distribution with mean 20 minutes and standard deviation 5 minutes.

1.Suppose the restaurant plans to expand its delivery network, and offers service to

commercial areas as well. A random sample of delivery times is required to estimate the

new population mean of delivery time. How large a sample is needed to ensure the

probability that the sample mean is larger than the new population mean by more than 2

minutes is less than 0.05? Assume the new population standard deviation is 10 minutes.