Last year, Brinkman Company had 20,000 units in its ending inventory. In this current year, Brinkman's variable production costs were $12 per unit. The fixed manufacturing overhead cost was $8 per unit in the starting inventory. The company's net income for the year was $9,600 higher under variable costing than it was under absorption costing. Provided these facts, Evaluate the number of units of product in the starting inventory last year.