The static budget, at the beginning of the month, for La Verne Company follows: Static budget: Sales volume: 2,100 units: Sales price: $57 per unit Variable cost: $14 per unit: Fixed costs: $26,000 per month Operating income: $64,300 Actual results, at the end of the month, follows: Actual results: Sales volume: 1,800 units: Sales price: $58 per unit Variable cost: $16 per unit: Fixed costs $35,000 per month Operating income: $40,600 Calculate the sales volume variance for variable costs. OA. $4,200 F OB. $12,900 U OC. $12,900 F OD. $300 U