The number of parts used for the wheels is,
(300,000 wheels) x (2 parts/wheel) = 600,000
For the seats,
(600,000 seats) x (3 parts/seat) = 1,800,00
From the calculation above, the ratio of wheels to total number of parts is 0.25 which means that the overhead allocated for the wheels should be equal to $165,000. The rest of the money should be for Sam, totaling to $495,000.