The Following Standards for Variable Manufacturing Overhead Have Been Established

The following standards for variable manufacturing overhead have been established for a company that makes only one product:
$\begin{array}{|l|r|}\hline \text { Standard hours per unit of output } & 7.8 \text { hours } \\\hline \text { Standard variable overhead rate } & \$ 12.55 \text { per hour } \\\hline\end{array}$
The following data pertain to operations for the last month:
$\begin{array}{|l|r|}\hline \text { Actual hours } & 2,900 \text { hours } \\\hline \text { Actual total variable overhead cost } & \$ 36,975 \\\hline \text { Actual output } & 200 \text { units } \\\hline\end{array}$
What was the variable overhead efficiency variance for the month?

A) $0.
B) $16,817 unfavourable.
C) $580 unfavourable.
D) $17,397 unfavourable.