The difference between variable costing and absorption costing net operating incomes is caused by the treatment of fixed manufacturing overhead costs. In variable costing, fixed manufacturing overhead costs are treated as period expenses and are not included in the product cost. In absorption costing, fixed manufacturing overhead costs are included in the product cost and are expensed when the product is sold.To calculate the difference between variable costing and absorption costing net operating incomes, we first need to calculate the cost per unit under each method:Variable costing cost per unit:Direct materials $$25$Direct labor $$18$Variable manufacturing overhead $$3$Variable selling and administrative $$5$Total variable cost per unit $$51$Absorption costing cost per unit:Direct materials $$25$Direct labor $$18$Variable manufacturing overhead $$3$Fixed manufacturing overhead $($$$627,000-$: $57,000$ units$)=$ $$11$Variable selling and administrative $$5$Total cost per unit $$62$