Now we are to find the probability of receiving 10 calls in a 20-minute interval. It is given that, on average, 36 calls are received per hour, so this must be converted to a 20-minute interval.

We previously found that, on average, there are 0.6 calls per minute. To find the mean number of calls in a 20-minute interval, multiply the mean number of calls per minute by 20.

(20 minutes)(mean number of calls per minute)=20(_______)

=_______ calls per 20 minutes

Thus, on the same 20-minute time interval, we have = ________ and x = _________.