A large tank is filled with methane gas at a concentration of 0.650 kg/m3. The valve of a 1.50-m pipe connecting the tank to the atmosphere is inadvertently left open for twelve hours. During this time, 9.00 × 10-4 kg of methane diffuses out of the tank, leaving the concentration of methane in the tank essentially unchanged. The diffusion constant for methane in air is 2.10 × 10-5 m2/s. What is the cross-sectional area of the pipe? Assume that the concentration of methane in the atmosphere is zero.