An engine using 1.20 moles of an ideal gas initially at a volume of 24.6 L and a temperature of 400 K performs a cycle consisting of four steps: (1) an isothermal expansion at 400 K to twice its initial volume, (2) cooling at constant volume to a temperature of 240 K (3) an isothermal compression to its original volume, and (4) heating at constant volume to its original temperature of 400 K. Assume that Cv = 21.0 J/K. (a)Sketch the cycle on a Pv diagram. (Do this on paper. Your instructor may ask you to turn in your work.) This answer has not been graded yet b) Find its efficiency.