Cox Engineering performs cement core tests in its laboratory. The following standards have been set for each core test performed: Standard Hours or Quantity Standard Price or Rate Direct materials ..................................... 3 pounds $0.75 per pound Direct labor ............................................ 0.4 hours $12 per hour Variable manufacturing overhead ........ 0.4 hours $9 per hour During March, the laboratory performed 2,000 core tests. On March 1 no direct materials (sand) were on hand. Variable manufacturing overhead is assigned to core tests on the basis of direct labor hours. The following events occurred during March: 8,600 pounds of sand were purchased and used at a cost of $7,310. 840 actual direct labor hours were worked at a cost of $8,610. Actual variable manufacturing overhead incurred was $3,200.

17. The materials price variance for March is: A) $860 unfavorable B) $860 favorable C) $281 unfavorable D) $281 favorable 18. The materials quantity variance for March is: A) $ 900 favorable B) $1,950 favorable C) $1,950 unfavorable D) $ 900 unfavorable 19. The labor rate variance for March is: A) $4,578 unfavorable B) $1,470 unfavorable C) $4,578 favorable D) $1,470 favorable

Question 18 is the main problem that I need help to understand how to solve.