Problem:

A simple telephone system consists of two end offices and a single toll office to which each end office is connected by a 1-MHz full-duplex trunk. The average telephone is used to make five calls per 8-hour workday. The mean call duration is 6 min. Ten percent of the calls are long-distance (i.e., pass through the toll office). What is the maximum number of telephones an end office can support? (Assume 4 kHz per circuit, and note that you may need to do some additional readings about transmission media and telephone systems).

Additional Information:

This question is from Computer Science as well as particularly to Networking. The question here is about computations of number of calls being transmitted through the telephone trunk line and number of phones which are making the calls.