Robinson's demand for pineapples is given as Q = 40 - 4P while Friday's is Q = 20 - P. Supply is given as Qs = 6 + P, and Pc = $1.
Find equilibrium price, equilibrium quantity, and the amounts Robinson and Friday will both end up consuming.
Then- suppose Rob and Fri are actually dealing with a public good like fireworks (# of rockets) and they must consume the same quantity. Efficiency requires Robinson's willingness to pay + Friday's willingness to pay must = MRT. What is the new efficient Q, and what will Rob and Fri now each be willing to pay?