Ruby Company produces a chair for which the standard specifies 6 yards of material per unit. The standard price of one yard of material is $12.60. During the month, 4,400 chairs were manufactured, using 25.900 yards at a cost of $11.84 per yard. Determine the following: Enter favorable variances as negative numbers. $ a. Direct materials price variance b. Direct materials quantity variance c. Total direct materials cost variance