The standard cost of direct materials is 4 per kg and the standard quantity 2kg per unit of output. The actual cost is 3.80 per kg and the actual quantity used is 2.1kg per unit. 20,000 units are produced in the period. What is the direct materials price variance? OA. 8,000 favourable B. 8,400 adverse C. 8,000 adverse OD. 8,400 favourable