Vicade has 1,000 commercial video game machines in inventory produced at a cost of $400 each (60% variable and 40% fixed). The machines were to have been sold for $1,000 each. However, the machines currently contain a minor malfunction reducing their selling price to $150 each. The company could correct the malfunction at a variable cost of $250 each and then sell the machines for $550 each. For purposes of determining whether the machines should be reworked, what is the opportunity cost per unit?