Calculate the work done by 1 mole of an ideal gas in a piston fitted cylinder at the initial pressure of 24.83 atm pressure and 300 K to expand its volume to 10 litre if
(a) external pressure is reduced to 1 atm in single step
(b) external pressure is reduced to 5 atm in 1st operation and then 1 atm in next step
(c) gas is allowed to expand into an evacuated space of 10 litre