Before finding the probability of no calls in a 6-minute interval, we must first determine how many calls are expected to come in during this 6-minute interval.

We previously found that, on average, there are 0.6 calls per minute. To find the mean number of calls in a 6-minute interval, multiply.

(6 minutes)(mean number of calls per minute)=6(_____)

=_________ calls per 6 minutes

Thus, on this 6-minute time interval, we have = _______

and x = ________ .