Driver Company Ltd has set the following standards for the production of one unit of product. Normal production each month is 500 units Standard Costs per unit: Direct materials: 8kg at $6.50 per kg Direct labour: 4 hours at $7.00 per hour During June, actual production amounted to 420 units. All direct material was purchased and used this month. Actual costs amounted to: Direct material: 3500kgs at a total cost of $21875 Direct labour: 1720 hours at a total cost of $12212 Required: Determine the standard direct labour rate variance for June production O a. $200 U O b. $172 U O c. $280 U O d. $168 U