Division Big does have excess capacity to produce Product XX. The division can sell Product XX for $10 per unit outside the company. Variable costs are $6 per unit. Division Small wants to purchase Product XX from Division Big to use in Product ZZ. The selling price of Product ZZ is $25 per unit and variable costs to finish the product after the transfer are $12 per unit. An outside supplier will sell Product XX for $12. What is the minimum transfer price for Division Big?