4. Reach Bummer Corporation has fixed manufacturing cost of $12 per unit. Consider the three independent cases that follow. Case A: Absorption- and variable costing income each totaled $240,000 in a period when the firm produced 18,000 units. Case B: Absorption-costing income totaled $320,000 in a period when finished-goods inventory levels rose by 7,000 units. Case C: Absorption-costing income and variable-costing income respectively totaled $220,000 and $250,000 in a period when the beginning finished-goods inventory was 14,000 units. Required: A. In Case A, how many units were sold during the period? B. In Case B, how much income would Beach Bum report under variable costing? C. In Case C, how many units were in the ending finished-goods inventory?