The university is considering level of light on campus. Tim, Shirley and Cynthia are the only students who work on campus. Tim's Marginal Benefit MB = 60 - 3Q, Shirley's MB = 20 - Q, and Cynthia's MB = 5, where Q is the level of light. If there are no fixed costs and the marginal cost of providing light is MC = 21, what is optimal brightness level of light?
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