Global AirSpan Freightways can earn $4 revenue per ton/mile on all US domestic routes, including the LAX-JFK route that requires a new airplane. (Thus, Global AirSpan Freightways collects 4*2139 = $8,566 for each ton flown between LAX and JFK.) Competitive pressures, however, keep Global AirSpan Freightways prices lower on all international routes, including the NRT-SIN route discussed here, where it earns only $2 in revenue for every ton/mile. Exactly how many ton/miles would an airplane need to carry on an international route each month, such that Global AirSpan Freightways would be completely indifferent to the issue of whether that airplane were a Boeing 747-400 or a Boeing 767-300 ?