The amount of time a bank teller spends with each customer has a population mean of 3.1 minutes and standard deviation of 0.4 minute. If you select a random sample of 16 customers,A) What the probability that the mean time spent per customer is at least 3 minutes?B) There is an 85% chance that the sample mean is less than how many minutes?C) What assumption must you in order to solve a) and b)?D) If you select a random sample of 64 customers, there is an 85% chance that the sample mean is less than how many minutes?