8. Sea Lanes Shipping Services Ltd. operates docks at Tocopilla, Chile, and provides ships to transport ore for the San Carlos Copper Mine nearby. Currently, only 1 dock is used for loading ore ships. Ore transport ships that are to be loaded arrive at the port at an average rate of 5.0 ships per week (7 days). The loading time per ship is distributed according to a negative exponential distribution with a mean of 1 day per ship.

a. What is the mean number of ships waiting to be loaded?

b. What is the mean time a ship spends in the system?

c. If the cost of an idle day for each ship is $4,500 and the cost of providing ore-loading docks is $900 per day for each dock, how many docks, if any, should the company add? (Use Figure 15.5.)