MNO produces a single product. The standard production requirement for each unit requires 2 kilograms of a single material at a standard cost of $4 per kilogram. During the last year, MNO purchased 10,000 kilograms of materials at total cost of $54,000. Also last year, MNO manufactured 3,000 units of product using a total of 7,500 kg. What was the MNO's materials quantity variance for the year?

a)nill

b) $6000 favourable

c) $4000 unfavourable

d) $6000 unfavourable