In the figure below, the change in internal energy of a gas that is taken from A to C along the blue path is +815 J. The work done on the gas along the red path ABC is -445 J.
(a) How much energy must be added to the system by heat as it goes from A through B to C?
(b) If the pressure at point A is five times that of point C, what is the work done on the system in going from C to D?
(c) What is the energy exchanged with the surroundings by heat as the gas goes from C to A along the green path?
(d) If the change in internal energy in going from point D to point A is +515 J, how much energy must be added to the system by heat as it goes from point C to point D?