Prior to a daytime VFR cross-country flight of 180 nautical miles on a true course of 090° with a true airspeed of 120 knots and a fuel burn of 10 gallons per hour, the winds aloft forecast at the planned cruising altitude along the route is 270° at 20 knots. What is the minimum fuel requirement in gallons to legally complete the flight under 14 CFR part 91? (Disregard taxi, takeoff, and climb fuel.)