Variable manufacturing costs are $123 per unit, and fixed manufacturing costs are $55,000. Sales are estimated to be 4,000 units. If an amount is zero, enter " 0 ". Round intermediate calculations to the nearest cent and your final answers to the nearest dollar. a. How much would absorption costing operating income differ between a plan to produce 4,000 units and a plan to produce 5,000 units? $x b. How much would variable costing operating income differ between the two production plans