all fine
For 2, you can also note that the number of calls in a t minute period is poisson( \lamda * t) . (you end up with exactly the same calculation)
During business hours, the number of calls passing through a particular cellular relay system averages 5 per minute.
(a)
Find the probability that no call will pass through the relay system during a given minute.
(b)
Find the probability that no call will pass through the relay system during a given 2 minute period.
Not so sure about this one.
(c)
Find the probability that 3 calls will pass through the relay system during a given minute.
Correct?