A unit mass of a substance undergoes an irreversible process from state 1 to state 2 while gaining heat from the surroundings at temperature T in the amount of q. If the entropy of the substance is S1 at state 1, and s2 at state 2, the entropy change of the substance As during this process is: a) As < S2 - S1 b) As > S2 - S1 c) As = S2 - Si d) As = S2 -S1+q/T