Probability (Binomial distribution (?))

I've been stuck with this exercise for a while now and can't really find the right approach to solving it, here it is:

The average number of phone calls per minute is 1.2, what would the probability of receiving say 2 phone calls in one minute?

I've tried solving this using binomial distribution, but couldn't really find a suitable "n". I've also tried taking the average (1.2) as the expected value E(x) but ended up even worse :sick: ...which lead me to think I'm approaching it completely the way.

Any help is appreciated.
Thanks.

The phenomenon of waiting lines is suitably described by the Poisson distribution. The result is p(k = 2) = 0,2168.

http://img87.imageshack.us/img87/3719/poisson9eh.th.jpg

Rui

thanks for the explanation, I did some research on the Poisson distribution, interesting, interesting lol... :thumb: