D(x) is the price, in dollars per unit. that consumers are willing to pay for x units of an item, and S(x) is the price, in dollars per unit, that producers are willing to accept for x units. Find (a) the equilibrium point, (b) the consumer surplus at the equilibrium point, and (c) the producer surplus at the equilibrium pornt. D(x) = 4000 30x, S(x) = 850 + 15x