A study-aid desk staffed by a graduate student has been established to answer students’ questions and help in working problems in your OSCM course. The desk is staffed eight hours per day. The dean wants to know how the facility is working. Statistics show that students arrive at a rate of four per hour and the distribution is approximately Poisson. Assistance time averages 10 minutes, distributed exponentially. Assume population and line length can be infinite and queue discipline is FCFS.
a. Calculate the percentage utilization of the graduate student.
b. Calculate the average number of students in the system, excluding the graduate student service.
c. Calculate the average time in the system.
d. Calculate the probability of four or more students being in line or being served.
e. Before a test, the arrival of students increases to six per hour on the average. What will the new average line length be?

Richardson hired j.c. flood company, a plumbing contractor, to correct a stoppage in the sewer line of her house. the plumbing company's 'snake' device, used to clear the line leading to the main sewer, became caught in the underground line. to release it, the company excavated a portion of the sewer line in richardson's backyard. in the process, the company discovered numerous leaks in a rusty, defective water pipe that ran parallel with the sewer line. to meet public regulations, the water pipe, of a type no longer approved for such service, had to be replaced either then or later, when the yard would have to be excavated again. the plumbing company proceeded to repair the water pipe. though richardson inspected the company's work daily and did not express any objection to the extra work involved in replacing the water pipe, she refused to pay any part of the total bill after the company completed the entire operation. j.c. flood company then sued richardson for the costs of labor and material it had furnished. (c) for what, if anything, should richardson be liable? explain."