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\mathrm{.}71$ per hour

Variable overhead

$3$ hours per unit at $$1\mathrm{.}98$ per hour

Actual Costs

Total variable cost, $$17,900$

Total fixed cost, $$8,000$

The variable factory overhead controllable variance is

a$.$ $$3,050$ favorable

b$.$ $$0$

c$.$ $$3,050$ unfavorable

d$.$ $$2,440$ favorable