Modify Model 12-3 from Section 12.5.1 to demand, in addition to the 95% confi dence-interval half width on the expected average total WIP being no more than 0.4, that the half width of the 95% confi dence intervals on expected average total time in system (for all part types combined) be no more than 3 minutes. One way to do this is to modify the Decide module in Figure 12-10 by adding an additional Condition to keep replicating (that is, dispose of the checking entity) if any half width is still too big.