25 Reconsider Problem 24. Suppose that at the beginningof year 1, power plants 1–4 have been constructed and are in operation. At the beginning of each year, PSI may shut down a plant that is operating or reopen a shut-down plant The costs associated with reopening or shutting down a plant are shown in Table 105. Formulate an IP to minimize the total cost of meeting the demands of the next five years.
(Hint: Let

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= Xit 1 if plant i is operated during year Yi = 1 if plant i is shut down at end of year t Z = 1 if plant i is reopened at beginning of year t You must ensure that if X = 1 and X+1 = 0, then Yi = 1. You must also ensure that if X-1 = 0 and Xi = 1, then Z = 1.) ==