Mines `A’ and `B’ are at a distance of 10 kms and 15 kms from the factory. The cost per tonne-km incase of mine A is Rs. 3 while it is R. 2.5 in case of mine B. The factory should procure coal from------------

• A. Mine A only
• B. Mine B only
• C. Both from mines A and B in the ration of 3: 2
• D. Can’t decide.