Standard material cost of a product is Rs. 20/-@ Rs. 10 per kg. In one batch, on an average the consumption of material was 1.8 kg and rate of material was Rs. 12 per kg. What is the material usage variance?
(a) Rs. 2/- adverse
(b) Rs. 2/- favorable
(c) Rs. 2.40 favorable
(d) Rs. 1.60 adverse