A salesperson has a 20% probability of selling a product during each call. The average rate of calls made per hour is 20 and follows a Poisson distribution.
a) Find the probability that there are 3 sales made in a period of 15 minutes. b) Find the probability that it takes more than 20 minutes to make 3 sales.
For the first one, do I simply say the average # of sales per hour is 20/100 * 20 = 4, and then just assume that it follows a Poisson distribution?
For the 2nd part, I have to use the exponential distribution somehow but I'm not sure precisely what to do.