For a certain product, the net contribution can be seen as Net Contribution = $500,000Q - $200,000, where Q is the market share. The expected market share (E(Q)) is then substituted into the net contribution equation--> E(Net Contribution) = $500,000E(Q) - $200,000.
Why can this be done? In other words, the expected net contribution is the sum of all possible contribution values (ContValue) times their associated probability value--> E(Net Contribution) = SUM(ContValue x P(ContValue)). Thus, the question is why does SUM(ContValue x P(ContValue)) = $500,000E(Q) - $200,000?