Parts arrive at a two-machine system according to an exponential interarrival distribution with mean 20 minutes. upon arrival, the parts are sent to machine 1 and processed. the processing-time distribution is tria (4.5, 9.3, 11) minutes. the parts are then processed at machine 2 with a processing-time distribution as tria (16.4, 19.1, 20.8) minutes. the parts from machine 2 are directed back to machine 1 to be processed a second time (same processing-time distribution but an independent draw from it). the completed parts then exit the system. run the simulation for a single replication of 20,000 minutes to observe the average number in the machine queues and the average part cycle time with arena model