The post office uses a multiple channel queue, where customers wait in a single line for the first available window.  If the average service time is 1 minute and the arrival rate is 7 customers every five minutes, find, when two service windows are open, (Use Management Scientist, Make sure that l and m are in the same units). a.the probability both windows are idle.b.the probability a customer will have to wait.c.the average time a customer is in line.d.the average time a customer is in the post office.