Formula for blocked cellphone calls

Pb = __________(A^N * N) / N!(N-1)___________
       Sum(n=0 to N) ((A^n / n!) + (A^N *N / N!(N-1))

Where

Pb: is Probability of a Blocked Call

A: call rate*call duration in units called Earlings named for A.K. Earling

N: Number of channels the line carries

n: number of callers

0 Remarks: