A large tank is filled with methane gas at a concentration of 0.730 kg/m3. The valve of a 1.20-m pipe connecting the tank to the atmosphere is inadvertantly left open for 19.0 hours. During this time, 9.60x10-4 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 2.10x10-5 m2/s. What is the cross-sectional area of the pipe? Assume that the concentration of methane in the atmosphere is zero.

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