Determine the change in the internal energy of a system that
( i ) absorbs 5 8 0 cal of thermal energy and 6 2 0 J of work is done by the system.
( ii ) releases 7 2 0 cal of thermal energy while 6 8 0 J of external work is done on the system.
( iii ) maintains at a constant volume while 1 4 3 0 cal of heat is removed from the system.