The market demand function for gadgets is qd.  The market is an undifferentiated Bertrand duopoly, where firm 1 is domestic, firm 2 is foreign, and both have a cost function C(q).
    In a free-market equilibrium, what is the output of each firm?  What is the total producer surplus? What is the total consumer surplus?
    If suppose that the government decides to charge the foreign producer a tariff of 1 (or 2) per gadget, what will be the condition?