The per-unit standards for direct materials are 2 gallons at $4 per gallon. Last month, 11,200 gallons of direct materials that actually cost $42,400 were used to produce 6,000 units of product. The direct materials quantity variance for last month was

Select one:

$3,200 favorable.

$2,400 favorable.

$3,200 unfavorable.

$5,600 unfavorable.

please give explanation on problem