A company developed the following per-unit standards for its product: 5 kilograms of direct materials at $3 per kilogram. Last month, 1,000 kilograms of direct materials were purchased for $2,900. Also, last month, 700 kilograms of direct materials were used to produce 135 units. What was the direct materials quantity variance for last month? a. $900 favourable b. $900 unfavourable c. $75 favourable d. $75 unfavourable