A sample of an ideal gas is taken through the cyclic process abca . It absorbs 50 J of heat during the part ab, no heat during bc and rejects 70 J of heat during ca. 40 J of work is done on the gas during the part bc.(a) find the internal energy of the gas at b and c if it is 1500 J at a. (b) calculate the work done by the gas during the part ca.