The standard budget for raw material costs of a product is 5 kg at 10 = 50 for a given period. At the end of a budget period, it shows that 4,500 kg was purchased at 10.50 per kg. Of this purchased quantity, 4,000 kg was actually used to manufacture 750 products. The unfavorable efficiency volume variance is:

a) 7,875 b) 7,500 c) 2,625 d) 2,500