1. A firm plans to sell 1,000 units of its only product at a price of $20 per unit, with variable manufacturing costs of $8 per unit and fixed manufacturing costs of $2 per unit. 
2. Expected SGA costs were $3 per unit (variable) and $1 per unit (fixed). 
3. Actual sales were 1,280 units.

What was the firm's sales volume variance?