A shopkeeper bought three varieties A, B and C of rice in different amounts at the rates of Rs. 34.50, Rs. 28.60 and Rs. 32.40 per kg respectively. In which of the following transactions will he gain maximum? (a) He bought 25 kg of rice of variety C and sold at Z 42 per kg and he bought 30 kg of variety A and sold at 38 per kg. (b) He bought 40 kg of rice of variety B and sold at RS. 37 per kg and he bought 20 kg of variety A and sold at Rs. 40 per kg. (c) He bought 20 kg of rice of varieties A and C each and sold at Rs. 38 and Rs. 36 per kg respectively. (d) He bought 30 kg of rice of variety A and sold at Rs. 37 per kg and he bought 20 kg of variety B and sold at Rs. 33 per kg. (e) He bought 20 kg of rice of variety B and sold at Z 40 per kg and he bought Rs. 40 kg of variety C and sold at Rs. 38 per kg.