Paper Three : Q8 (ii)

Two nuclei A and B on the downslope of the BE per nucleon with nucleon number graph will produce C further down the slope (smaller BE compared to B +C ) . Bearing in mind that smaller BE means mass of C is greater in mass than A+B. If you put all three in a equation, A+B = C you will need to balance the equation with E(energy). Hence E + A + B = C, energy needs to be supplied to A and B to produce C.