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This answer results from not deducting the variable selling and administrative costs.
This answer results from multiplying the variable manufacturing cost per unit and the variable selling and administrative cost per unit by the number of units produced instead of by the number of units sold.
Under variable costing, all of the fixed factory overheads will be expensed during the period. The manufacturing contribution per unit is calculated as the sales price ($10) minus the variable costs of production ($5.50) and is $4.50. Since they sold 1,000 units, this gave them $4,500 of manufacturing contribution margin. Variable selling and administrative costs are $.50 per unit sold. Therefore, the contribution margin (sales revenue minus all variable costs, including both manufacturing and non-manufacturing) is thus $4.50 per unit minus $.50 per unit, or $4.00 per unit, which equals $4,000 in total. Fixed manufacturing ($1,200) and fixed selling ($1,000) costs are subtracted from the contribution margin, giving us a net operating income of $1,800 ($4,000 ? $1,200 ? $1,000).
This answer results from multiplying the variable manufacturing cost per unit by the number of units produced instead of by the number of units sold.