Suppose rain is falling at an average rate of 30 drops per square inch per minute.
a. What is the probability that a particular square inch is hit by exactly 4 drops in the next 10-second period?
b. How many 10-second intervals do you expect to observe this square inch until you find a 10-second interval with exactly 4 raindrops?
c. What is the probability you would have to observe ten 10-second intervals to find three of them with exactly 4 raindrops?