The amount oltime lhat a driveethrougn bank teller spends on a customer is a random variable With a mean p : 7 4 minutes and a standard deviation 6 : 3 2 minutes if a random sampte of 64 customers is observed, nd Ihe probability that their mean time al the tetler's window is (a) at most 6 8 minutes; (b) more than 7' 8 minutes, (c) at teast 7,4 minutes but less lhan 8 2 minutes, Click here to view page 1 of the standard normal distribution table Click here to View page 2 of the standard normal distribution taple (a) The probability that Ihe mean time is al most 6.8 minutes is (Round to four decimal places as needed ) (b) The probability that Ihe mean time is more than 7 B minules i5 (Round In four decimal places as needed ) (c) The probability that the meantime IS between 74 minutes and 82 minutes is (Round to four decimal places as needed )