Air in the piston–cylinder device in the figure is compressed from state 1 to state 2 following PV^{1.3} = constant. Take R = 0.287 kJ/kg·K and c_{v} = 0.718 kJ/kg·K for air. Determine (a) the work done on the air (answer in kJ), (b) the change in internal energy of the air (answer in kJ) and (c) the heat transfer, stating its direction (answer in kJ).