Indre works on reception in an office and deals with all the telephone calls that arrive. Calls arrive randomly and, in a 4-hour morning shift, there are on average 80 calls.
Using a suitable model, find the probability of more than 4 calls arriving in a particular 20 -minute period one morning.
Indre is allowed 20 minutes of break time during each 4-hour morning shift, which she can take in 5 -minute periods. When she takes a break, a machine records details of any call in the office that Indre has missed.
One morning Indre took her break time in 4 periods of 5 minutes each.
Find the probability that in exactly 3 of these periods there were no calls.
On another occasion Indre took 1 break of 5 minutes and 1 break of 15 minutes.
Find the probability that Indre missed exactly 1 call in each of these 2 breaks.