Find the indicated probabilities using the geometricdistribution, the Poissondistribution, or the binomial distribution. Then determine if the events are unusual. Ifconvenient, use the appropriate probability table or technology to find the probabilities.

Assume the probability that you will make a sale on any given telephone call is 0.21. Find the probability that you(a) make your first sale on the fifthcall, (b) make your sale on thefirst, second, or thirdcall, and(c) do not make a sale on the first three calls.

(a) P(make your first sale on the fifth call)=

nothing

(Round to three decimal places asneeded.)