One mole of an ideal monatomic perfect gas at 10atm and 200K is to be transformed to 0.15atm and 900K. Calculate S1,S2, and the total entropy change for the system which occurs along each of the following two-step reversible paths: a. Isobaric expansion and isochoric temperature drop. b. Isobaric expansion and adiabatic temperature drop. c. Isothermal expansion and isochoric temperature increase. d. Isothermal expansion and isobaric temperature increase