Midgley Corporation makes a product whose direct labor standards are 1.0 hours per unit and $11.00 per hour. In April, the company produced 5,100 units using 4,800 direct labor-hours. The actual direct labor cost was $50,880. The labor efficiency variance for April is:

a. $3,300 U

b. $3,300 F

c. $3,219 F

d. $3,328 U