Students are queued up at the registrar’s office when the registration windows open at 8 a.m. There are four open windows; students approach the first open window as they advance to the front of the queue. Assume that 10% of the students require 5 minutes of service time, 30% of the students require 7 minutes of service time, 40% require 10 minutes, and 20% require 15 minutes. Simulate the service of the first 20 students in a random queue. Show the schedule of service at the four windows (A, B, C, D), determine how long it takes to process these students, and give the average time from 8 a.m. to leaving the service window.