Sheffield Company has a materials price standard of $2.50 per kilogram. 3970 kilograms of materials were purchased at $2.10 a kilogram. The actual quantity of materials used was 3580 kilograms, although the standard quantity allowed for the output was 3400 kilograms. Sheffield Company's materials quantity variance is

$1360 U. $450 U. $1360 F. $450 F.