$(30$ pts$)$ Draw a logical model $($network$)$ for the following system. Specify all the details on the network.

Parts arrive at a CNC for machining. The interarrival time is exponentially distributed with mean value $8$ minutes. The parts wait for processing on a fist$-$in$-$first$-$out basis. The processing time per part is exponentially distributed with mean processing time $3$ minutes. After a part has been processed it is accepted with probability $0\mathrm{.}6$ or rejected with probability $6\mathrm{.}4.$ Rejected parts are placed in the queue of umprocessed parts, after a delay of $15$ seconds.