One mole of an ideal gas at T = 25 °C is held in a cylinder by a piston at a pressure of 1 x 10^7 Pa. The piston pressure is released in three stages, first to 5 x 10^6 Pa then to 1 x 10^6 Pa, and then to 1 x 10^5 Pa Calculate the work done by the gas during these irreversible, isothermal expansions.