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Q4. (10 points) Consider the following payoff table in which D1 through D4 represent decisions, S1 through S4 represent states of nature, and the values in the cells represent profits. S1 S2 S3 S4 D1 -20 40 60 100 D2 30 120 60 -50 D3 30 30 40 40 D4 10 -60 80 70 Required a) The optimal decision under the maximax criterion is: b) The optimal decision under the minimax regret criterion is: c) The optimal decision under the maximin criterion is: d) Suppose that the probabilities of states of nature 52 and 53 occurring are equal and that the probability of state of nature S4 occurring is .50. If the probability of state of nature S1 occurring is three times the probability of state of nature S2 occurring, the optimal decision under the expected value criterion is