The following materials standards have been established for a particular product: Standard quantity per unit of output.......6.9 pounds Standard price...............................$17.70 per pound The following data pertain to operations concerning the product for the last month: Actual materials purchased...............6,200 pounds Actual cost of materials purchased.....$113,460 Actual materials used in production.......5,700 pounds Actual output....................................700 units What is the materials quantity variance for the month? a. $9,150 U b. $8,850 U c. $15,921 U d. $15,399 U