Exercise 9.13 This is a continuation of Exercise 6.8 (page 278).

(a) When an alarm is observed, a decision is made whether to shut down the reactor. Shutting down the reactor has a cost cs associated with it (independent of whether the core was overheating), whereas not shutting down an overheated core incurs a cost cm, which is much higher than cs. Draw the decision network modeling this decision problem for the original system (i.e., only one sensor). Specify any new tables that must be defined (you should use the parameters cs and cm where appropriate in the tables). You can assume that the utility is the negative of cost.

(b) For the decision network in the previous part, determine the expected utility of shutting down the reactor versus not shutting it down when an alarm goes off. For each variable eliminated, show which variable is eliminated, how it is eliminated (through summing or maximization), which factors are removed, what factor is created, and what variables this factor is over. You are not required to give the tables.