Please explain the solution to this general problem with accurate principles.

Everton Inc. has a direct labor standard of 3.5 hours per unit of output. Each employee has a Standard wage rate of $14.00 per hour. During March, Everton paid $117,600 to employees for 8,400 hours worked. The company produced 2,500 units during March. What is the direct labor efficiency variance? a) $7,000 unfavorable b) $6,300 favorable c) $6,300 unfavorable d) $4,900 favorable