The work involved () in an isothermal expansion of moles of an ideal gas from an initial pressure of — Thermodynamics and Thermochemistry Chemistry Question

Question

The work involved ($w$) in an isothermal expansion of $n$ moles of an ideal gas from an initial pressure of '$P$' atm to final pressure of 1 atm in number of steps such that in every step the constant external pressure exactly 1 atm less than the initial pressure of gas is maintained, is given as