All trucks traveling on I-75 south of Ocala, Florida, must stop at a weigh station. This station has one set of scales, which can weigh an average of 18 trucks an hour, exponentially distributed. Trucks arrive at the weigh station at an average of 15 an hour, Poisson distributed.

a. What is the average delay a truck suffers at the 1-75 weigh station? That is, what is the average total time the truck spends waiting and being weighed?

b. What is the probability that an arriving truck has to wait?

c. On average, how many trucks are waiting in line at the I-75 weigh station?

d. On average, how many trucks are at the 1-75 weigh station?

e. What is the probability of no more than three trucks at the weigh station?