Demand in a market is represented by the equation, P = 50 - QD. Suppose the market price is $30. (a) How many units do buyers wish to purchase in this market? (b) What is the maximum amount that the buyers are willing to pay for this quantity of output? (c) What is the actual amount that buyers have to pay for this quantity of output? (d) What is the consumer surplus that buyers obtain from purchasing this quantity of output?