Retriever company completed 2,250 units of its single product, consuming 4,650 labor hours that cost the firm $79,050. According to manufacturing specifications, each unit should have required 2 hours of labor time at $18 per hour.

The company's labor efficiency variance is :

A. $4,650 F

B. $2,700 F

C. $4,650 U

D. $2,700 U

E. None of these