Maximum profit calculation

Hello Sir John.
i jst want to know if return per factory hour is given in the question and they want us to calculate maximum profit then we calculate maximum profit by taking return per factory hour and multiply it by total hours to produce the units? is it true? because normally we 1st calculate sales revenue then minus direct material cost and thn minus fixed cost/ factory cost and thn we gt profit figure. what is the right way? actully i am doing bpp kit question 16 thin Co and i am little bit confused in calculating profit.i did by using sales – directmaterial -fixed cost approach and in the bpp kit they use return per factory hour and multiply by total hours required to produce the units.