Calculate the work done in Joules (for each case) when one mole of an ideal gas, initially at P = 9atm, T = 298K is expanded isothermally to P=1atm if

a.) the expansion proceeds against a constant external pressure Pext = 1atm

b.) the external pressure is reduced in steps, from Pext = 9atm to 7atm, then from 7atm to 5atm, then from 5atm to 3atm, and from 3atm to 1atm.

c.) the expansion is done reversibly. Which expansion extracts the maximum work from the gas?