Bondi Corporation makes automotive engines. For the most recent month, budgeted production was $3,200$ engines. The standard power cost is $$2\mathrm{.}30$ per machine$-$hour. The company's standards indicate that each engine requires $11\mathrm{.}0$ machine$-$hours. Actual production was $3,500$ engines. Actual machine$-$hours were $36,610$ machine$-$hours. Actual power cost totaled $$91,748.$

Required:

Determine the rate and efficiency variances for the variable overhead item power cost. $($Indicate the effect of each variance by selecting $"$F$"$ for favorable, $"$U$"$ for unfavorable, and "None" for no effect $($i$.$e$.,$ zero variance$).$ Input all amounts as positive values.$)$