The materials budget for producing 5,000 units of product is 25,000 litres at $3.30 per litre. In the first month of production the company purchased 30,000 litres at a cost of $105,000, of which 28,000 litres were used to produce an actual output of 5,900 units. What was the material usage variance? a. $650 adverse b. $5,250 favourable c. $4,950 favourable d. $9,900 adverse