设银行有四个服务窗口，一个等待队列, 每个窗口均可以办理存款、取款、挂失、还贷业务，每种业务所需的服务时间不同，客户到达银行后，先到打号机上打号，号票上包括到达时间、编号和需要办理的业务，然后在银行内等候, 当任一服务窗口空闲时,处理等候客户中排在最前面的客户的业务。写一个上述银行业务的模拟系统,通过模拟方法求出客户在银行内逗留的平均时间和每个窗口办理的客户数及办理的每种业务数(A bank has four service windows, a waiting queue, each window can make deposits, withdrawals, loss, loan business, every business needs Business Hours, bank customers arrive after the first marking machine marking number on the ticket, including the need to handle the business, number and time of arrival then, waiting at the bank, when any service window is idle, waiting for processing customers ranked top in the customer's business. Write a simulation system for the above banking business, and find out the average time of customers' stay in the bank and the number of customers handled by each window and the number of business handled by simulation.)