Consider the following simplified scenario. Imagine that the Australian national rugby union (for short, Rugby AU) has exclusive rights to organize the games played by the national team. Rugby AU decides that the next match, between the Wallabies and the All Blacks (i.e., the Australian and the New Zeeland national rugby teams), will be hosted at the Marvel Stadium in Melbourne. Rugby AU has no fixed costs for organizing the game, but it must pay a marginal cost MC of $20 per seat to the owners of the Marvel Stadium. Two types of tickets will be sold for the game: concession and full fare. Based on any official document that attests to their age, children and pensioners qualify to purchase concession tickets that offer a discounted price; everyone else pays the full fare. The demand for full-fare tickets is QF(P) = 120 2P. The demand for concession tickets is QC(P) = 80 2P.

The government wants to encourage children and pensioners to attend sport events. To do so, it is willing to give Rugby AU a subsidy of s per concession ticket sold, but the government wishes to calibrate this subsidy such that Rugby AU will sell the same number of concession tickets as in perfect competition. Assuming that the government knows the demand and the costs that Rugby AU has, compute how much the subsidy s should be.