Methane escapes through a small (10^(-7) m^2) hole in a 10-m^3 tank. The methane escapes so slowly that the temperature in the tank remains constant at 23?C. The mass flow rate of the methane through the hole is given by m=0.66 pAv(RT), where p is the pressure in the tank, A is the area of the hole, R is the gas constant, and T is the temperature in the tank. Calculate the time required for the absolute pressure in the tank to decrease from 500 to 400 kPa.