A helium-filled balloon of the type used in long-distance flying contains 420, 000 ft^3 (1.2 times 10^7 L) of helium. Suppose you fill the balloon with helium on the ground, where the pressure is 741 mm Hg and the temperature is 24.4 degree C. When the balloon ascends to a height of 2 miles, where the pressure is only 600. mm Hg and the temperature is -33 degree C, what volume is occupied by the helium gas? Assume the pressure inside the balloon matches the external pressure.