so that, in both inspections, only half of what had failed before now really fail, and the others have returned for a re-do and the preceding operation (that is, to the Sealer and Rework for the f rst and second inspections, respectively). The redone parts still have to be reinspected with the same probabilities for what happens to them there as for parts arriving there for the f rst time. There’s no limit on the number of redos in either place. (HINT: Explore the Help topic in the Decide modules and think about a three-sided coin.) Compare the results (making 100 replications) to Model 4-1, looking at the total times in system of the three different exit possibilities (shipped, salvaged, and scrapped).