The auxiliary bookstore in the student center has one checkout counter where one employee operates the cash register. Customers arrive at a rate of 24 per hour following a Poisson distribution and service times are exponentially distributed, with a mean rate of 30 customers per hour. The average purchase per customer is $48. The bookstore considers adding another employee to assist the present operator. There are several options to utilize this additional staff. One is to enable more customers to be served in less time, thus increasing the service rate from 30 customers per hour to 40 customers per hour. Alternatively, the bookstore could redesign to add a second cash register, one has its own line. Assume existing customers split evenly between the two cash registers and each has her/his own line, just like most grocery stores. Finally, the bookstore can use this additional staff as a second register but unlike option 2, there is only one combined line shared by these two registers (like most of the bank tellers). Assume the hourly rate for each employee is $20, regardless what job do they perform. Assume that each customer is only waiting for up to 1 minute to be served, or would renege (i. e., leave the store unpurchased). Which option should the bookstore adopt to minimize the total cost?