In the last four$-$week period, the $20$ sales staff in the telephone sales department of a

company made $14100$ calls to potential customers.

The standard time for a call is $10$ minutes and the staff work a $35$ hour week, of which five

hours are made up of rest or breaks. The standard cost per call is $$5\mathrm{.}00.$

What is the labour efficiency variance for the last four$-$week operating period?

$$1500$ Favourable

$$1500$ Adverse

$$13500$ Favourable

$$13500$ Adverse