The standard costs and actual costs for factory overhead for the manufacture of $2,700$ units of actual production are as follows:

Standard Costs

Fixed overhead $($based on $10,000$ hours$)$

Variable overhead

$3$ hours per unit at $$0\mathrm{.}70$ per hour

$3$ hours per unit at $$2\mathrm{.}09$ per hour

Actual Costs

Total variable cost, $$18,100$

Total fixed cost, $$8,200$

The total factory overhead cost variance is

a$.$ $$1,171$ unfavorable

b$.$ $$2,501$ favorable

c$.$ $$2,501$ unfavorable

d$.$ $$3,831$ favorable