Suppose Andy's and Ben's marginal benefits (in dollars) from a neighborhood water fountain are given as follows: Andy: MB = 30 - 2Q for Q 15; MB = 0 for Q > 15 Ben: MB = 20 - Q for Q 20; MB = 0 for Q > 20 where Q denotes the diameter of the fountain to be installed. Suppose that Q = 16.9m, the marginal benefit of an additional unit of the diameter of the fountain to the society is [Answer] dollars. (In decimal numbers, with two decimal places, please.) Answer: Question 11