Swifty Company has a materials price standard of $2.40 per kilogram. 3990 kilograms of materials were purchased at $2.10 a kilogram. The actual quantity of materials used was 3630 kilograms, although the standard quantity allowed for the output was 3530 kilograms. Swifty Company's total materials variance is

A) $100 F.

B)$8513 U.

C)$9570 U.

D)$957 F.