MNO produces a single product. The standard production requirement for each unit requires 2 kilograms of a single material at a standard cost of $5 per kilogram. During the last year, MNO purchased 10,000 kilograms of materials at total cost of $58,000. Also last year, MNO manufactured 3,000 units of product using a total of 7,000 kg. What was the MNO's materials purchase price variance for the year?

a) Nill

b)$4000 favourable

c) $8000 unfavourable

d)$2800 unfavourable