Introduction to Management Science 12th Edition by Bernard Taylor

Exercise 5

The management of Dynaco Manufacturing Company (see Problem) likes to have its operators working 90% of the time. What must the assembly line arrival rate be for the operators to be as busy as management would like
Problem
The Dynaco Manufacturing Company produces a particular product in an assembly line operation. One of the machines on the line is a drill press that has a single assembly line feeding into it. A partially completed unit arrives at the press to be worked on every 7.5 minutes, on average. The machine operator can process an average of 10 parts per hour. Determine the average number of parts waiting to be worked on, the percentage of time the operator is working, and the percentage of time the machine is idle.