Statistics s2 poisson distribution

1. Incoming telephone calls to a school arrive atrandom times. The average rate will varyaccording to the day of the week. On Mondaymornings, in term time there is a constantaverage rate of 4 per hour. What is theprobability of receiving
(a) 6 or more calls in a particular hour,
(b) 3 or fewer calls in a particular period of twohours?
During term time on Friday afternoons theaverage rate is also constant and it is observedthat the probability of no calls being receivedduring a particular hour is 0.202. What is theaverage rate of calls on Friday afternoons?
I am stuck on the last part, do you just use the distribution table in the formula booklet.
Thanks in advance