A merchant buys 200 kg of rice at Rs.7.25 per kg, 400 kg of rice at Rs.5.75 per kg. He mixes them and sells one third of mixture at Rs.6 per kg. At what rate should he sell the remaining mixture so that he may earn a profit of 20% on the whole out lay?

• A. Rs.28.25 per kg                 
• B. Rs.13.25 per kg
• C. Rs.8.25 per kg     
• D. none of these