yield

suppose you take 100 moles of the reactant.

Then according to data only 58 moles of the next intermediate product will form.

After that 54% of this 58 moles will form . i.e. 31.32 moles

next there is 68% yield. So final no. of moles formed = 68% of 31.32 moles = 21.2976

So final percentage yield = 21.2976 %

BTW, what are (A) (B) (C)