The standard costs and actual costs for factory overhead for the manufacture of 2,500 units of actual production are as follows:

Standard Costs

Fixed overhead (based on 10,000 hours)3 hours per unit at $0.74 per hour

Variable overhead3 hours per unit at $1.93 per hour

Actual Costs

Total variable cost, $18,000

Total fixed cost, $8,200

The variable factory overhead controllable variance is

a.$2,820 favorable

b.$3,525 favorable

c.$3,525 unfavorable

d.$0