ProCart manufactures shopping carts which it sells directly to supermarkets at a unit price of $36. Salesmen complain that they are overworked, so management is considering hiring another salesman at a salary of $28,000, with an additional $12,000 budgeted for auto and travel expenses. If the unit variable cost percentage is 40%, how many units will the salesman need to sell before he contributes anything to manufacturing overhead and profit?