The static budget, at the beginning of the month, for Assembly Furniture Company follows: Static budget: Sales volume: 1,100 units; Sales price: $71.00 per unit Variable costs: $33.00 per unit; Fixed costs: $36,400 per month Operating income: $5,400 Actual results, at the end of the month, follows: Actual results: Sales volume: 980 units; Sales price: $75.00 per unit Variable costs: $36.00 per unit; Fixed costs: $33,500 per month Operating income: $4,720 Calculate the sales volume variance for fixed costs.