A cellular phone system services a population of n l "voice users" (those who occasionally need a voice connection) and n 2 "data users" (those who occasionally need a data connection). We estimate that at a given time, each user will need to be connected to the system with probability PI (for voice users) or P2 (for data users), independent of other users. The data rate for a voice user is rl bits/sec and for a data user is r 2 bits/sec. The cellular system has a total capacity of c bits/sec. What is the probability that more users want to use the system than the system can accommodate