An integrated petroleum company is considering expansion of its one unloading facility at its Australian refinery. Due to random variations in weather, loading delays, and other factors, ships arriving at the refinery to unload crude oil arrive according to the exponential distribution with an average arrival rate of 8 ships per week. Service time is also exponential with an average service rate of 12 ships per week. (a) What is the average number of ships waiting to gain access to the single unloading facility (15pts)? (b) What is the average time a ship must wait before beginning to deliver its cargo to the refinery (15pts)? (c) What is the average total time (waiting plus actual delivery) that a ship spends at the refinery