We are using a private branch exchange (PBX), a telephone switch, to connect our office building to the telephone company's central office. There are 50 telephones in the building, and each telephone is used on average 5% of the workday to make calls to/from phones outside the building. The PBX enables us to connect telephones inside the building without having to use the services of the telephone company. Telephone calls to/from phones outside the building are connected by the central office. We want to determine the required capacity of the line between the PBX and the telephone company's central office, expressed as a multiple N of the bandwidth required for each phone call. Required:
Calculate the probability that a call will be blocked due to not enough capacity between the PBX and the central office.