Zippy-Lube is a drive-through automotive oil change business that operates 10 hours/day and 6 days/wk. Cars arrive randomly at the oil change center following a Poisson distribution at a rate of 3.5 cars/hr. After reviewing the historical data, the owner of Zippy-Lube has determined that the average service time per car is 15 minutes with a standard deviation of 2 minutes. Determine: a. The probability that the system is empty. b. The expected total time that a car spends in this system (waiting in line and being served).