The owner of a franchise of gas stations is interested in determining how large the storage tank should be at a new station. Four gas pumps, all dispensing the same grade of fuel, will be installed to service customers. Cars arrive according to an exponential distribution with a mean of 0.8 minute. (We’ll assume that this is uniform throughout the station’s hours of operation.) Their time at the pump (from start to f nish) follows a triangular distribution with parameters 2, 2.8, and 4 minutes. The cars require varying amounts of fuel, distributed according to a triangular distribution with parameters 4, 7.5, and 15 gallons. kel01315_ch11_479-518.indd 514 05/12/13 3:19 PM Continuous and Combined Discrete/Continuous Models 515 Ref ll trucks arrive according to a uniform distribution with a minimum interarrival time of 6.75 hours and a maximum of 8.25 hours. They carry enough fuel to ref ll the storage tank and do so at a rate of 300 gallons per minute. If the storage tank empties before a ref ll truck arrives, the pumps are closed until the storage tank contains 100 gallons (from its next ref ll). For purposes of this analysis, assume that cars that are in-process when the tank empties can complete their service and that waiting cars will stay at the station until the pumps reopen. However, any cars that arrive while the pumps are closed will drive by to f nd another place to f ll up. Determine (to the nearest 100 gallons) the tank capacity that will result in fewer than 0.1% of cars balking due to closed pumps. 11-3 An earnest analyst for Grace Enterprises, the owner of the coal-loading operation described in Model 11-3, has become concerned that assuming that coal will always be available to load into the barges might not be realistic. She would like to ref ne the estimates of loading times and numbers of waiting barges by incorporating into her model the delivery of coal by train to the storage yard. Trains are scheduled to arrive every 8 hours throughout the day and night, and they’re usually on time. Each train carries 12,000 tons of coal, which is unloaded into the storage yard at a rate of 7,500 tons per hour. The storage yard can hold 17,000 tons of coal; for purposes of this analysis, cancel a train’s delivery if the yard is full at the train’s scheduled arrival time. Modify Model