Chilled MFG makes a single producta cooling coil used in commercial refrigerators. The company has a standard cost system in which it applies overhead to this product based on the standard machine-hours allowed for the actual output of the period. Data concerning the most recent year appear below:

Budgeted variable manufacturing overhead	$	30,000
Budgeted production (a)		25,000	units
Standard hours per unit (b)		0.50	machine-hours
Budgeted hours (a) (b)		12,500	machine-hours
Actual production (a)		22,000	units
Standard hours per unit (b)		0.50	machine-hours
Standard hours allowed for the actual production (a) (b)		11,000	machine-hours
Actual variable manufacturing overhead	$	30,160
Actual hours		10,400	machine-hours

The variable overhead efficiency variance is:

a. $,1398 F

b. $1,740 F

c. $1,440 F

d. $1,740 U