Suppose we have a competitive market for a good with domestic demand and supply given by:
P = 310 - .05QD
P = 30 + .03QS
International supply is given by a constant competitive price of P1 = $90.
Finally, suppose that there was no international supply, and that the domestic market given by the above equations was the only market for this good in the world. What export tariff could the government impose to create a global monopoly?