
Let initial moles of reactant taken =n
Total moles obtained for benzene sulphonic acid (with yield =60) =0.6n

Moles of benzene sulphonic acid before reaction II=0.6n
Moles obtained for phenol (with yield = 50) =0.6×0.5n=0.3n
So over all yield of complete reaction =n0.3n×100=30
