Culinary Kitchen Supply produces bamboo cutting boards. The standard material cost for the bamboo used in each lamp is $18 per square foot. Each board requires 3 square feet of bamboo. In August, the company produced 1,200 cutting boards. There were 3,400 square feet of bamboo used during the month. The bamboo used had an actual cost $20 per square foot. What was the materials quantity variance in August for bamboo?
A. $4,000 favorable
B. $3,600 favorable
C. $3,600 unfavorable
D. $4,000 unfavorable