In a quarry, trucks deliver ore from three shovels to a single crusher. Trucks are assigne...

In a quarry, trucks deliver ore from three shovels to a single crusher. Trucks are assigned to specific shovels, so that a truck will always return to its assigned shovel after dumping a load at the crusher. Two different truck sizes are in use, 20 and 50 tons. The size of the truck affects its loading time at the shovel, travel time to the crusher, dumping time at the crusher, and return-trip time from the crusher back to its shovel, as follows (all times are in minutes):

To each shovel are assigned two 20-ton trucks and one 50-ton truck. The shovel queues are all FIFO, and the crusher queue is ranked in decreasing order of truck size, the rule’s being FIFO in case of ties. Assume that at time 0 all trucks are at their respective shovels, with the 50-ton trucks just beginning to be loaded. Run the simulation model for 8 hours and estimate the expected time-average number in queue for each shovel and for the crusher. Also estimate the expected utilizations of all four pieces of equipment. Use streams 1 and 2 for the loading times of the 20-ton and 50-ton trucks, respectively, and streams 3 and 4 for the dumping times of the 20-ton and 50-ton trucks, respectively. [This problem is taken from Pritsker (1995, pp. 153-158).]