To find the original volume of gas, you can use the combined gas law equation: (P1V1)/T1 = (P2V2)/T2. Plug in the given values to solve for the original volume, where P1 = 135 kPa, V1 = 575 L, T1 = 295 K, P2 = 105 kPa, and T2 = 270 K. Solving for V1 will give you the original volume of the gas.