The standard costs and actual costs for factory overhead for the manufacture of $2,900$ units of actual production are as follows:

Standard Costs

Fixed overhead $($based on $10,000$ hours$)3$ hours per unit at $$0\mathrm{.}70$ per hour

Variable overhead

$3$ hours per unit at $$2\mathrm{.}05$ per hour

Actual Costs

Total variable cost, $$18,100$

Total fixed cost, $$8,200$

The fixed factory overhead volume variance is

a$.$ $$728$ unfavorable

b$.$ $$728$ favorable

c$.$ $$910$ unfavorable

d$.$ $$0$