Find the indicated probabilities using the geometric distribution, the Poisson distribution, or the binomial distribution. Then determine if the events are unusual. If convenient, 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 0.14 . Find the probability that you (a) make your first sale on the fifth call, (b) make your sale on the first, second, or third call, and (c) do not make a sale on the first three calls.
(a) $P$ (make your first sale on the fifth call $)=0.077$
(Round to three decimal places as needed.)
(b) $P$ (make your sale on the first, second, or third call) = (Round to three decimal places as needed.)

Step 1 ：Given that the probability of making a sale on any given call is 0.14, we are asked to find the probability of making a sale on the first, second, or third call.

Step 2 ：We can calculate this using the geometric distribution formula for each of the three calls and then adding the results together. The geometric distribution formula is: \(P(X = k) = (1 - p)^{(k - 1)} * p\), where \(p\) is the probability of success (in this case, making a sale), \(k\) is the number of trials until the first success, and \(P(X = k)\) is the probability of the first success occurring on the \(k\)th trial.

Step 3 ：Let's calculate the probability for each call: \(p = 0.14\)

Step 4 ：For the first call, the probability is \(0.14\)

Step 5 ：For the second call, the probability is \((1 - 0.14)^{(2 - 1)} * 0.14 = 0.1204\)

Step 6 ：For the third call, the probability is \((1 - 0.14)^{(3 - 1)} * 0.14 = 0.103544\)

Step 7 ：Adding these probabilities together gives us the total probability of making a sale on the first, second, or third call: \(0.14 + 0.1204 + 0.103544 = 0.363944\)

Step 8 ：Rounding to three decimal places, the final answer is \(\boxed{0.364}\)