10. An ideal gas, consisting of n moles, undergoes an irreversible process in which the temperature T has the same value at the beginning and end. If the volume changes from Vi to Vf, the change in entropy is given by: (A) nR ln(Vi/Vf) (B) nR ln(Vf/Vi) (C) nR (Vf/Vi) (D) nR (Vf−Vi) (E) none of the above (entropy can't be calculated for an irreversible process)