If the boundary of system moves by an infinitesimal amount, the work involved is given by `dw=-P_("ext")dV` for irreversible process `w=-P_("ext")DeltaV " "( "where "DeltaV=V_(f)-V_(i))` for reversible process `P_("ext")=P_("int")pmdP~=P_("int")` so for reversible isothermal process `w = -nRTln.(V_(f))/(V_(i))` 2mole of an ideal gas undergoes isothermal compression along three different plaths : (i) reversible compression from `P_(i)=2` bar and `V_(i) = 8L` to `P_(f) = 20` bar (ii) a single stage compression against a constant external pressure of 20 bar, and (iii) a two stage compression consisting initially of compression against a constant external pressure of 10 bar until `P_("gas")=P_("ext")`, followed by compression against a constant pressure of 20 bar until `P_("gas") = P_("ext")` Order of magnitude of work is :A. `w_(1) gt w_(2) gt w_(3)`B. `w_(3) gt w_(2) gt w_(1)`C. `w_(2) gt w_(3) gt w_(1)`D. `w_(1)=w_(2)=w_(3)`