A farmer mixes two brands P and Q of cattle feed. Brand P, costing Rs250 per bag contains 3 units of nutritional element A,2.5units of element B and 2units of element C.Brand Q costing Rs200 per bag contains 1.5units of element B and 3units of element C. The minimum requirements of nutrients A,B, and C are 18 units, 45 units and 24 units respectively. Determine the number of bags of each brand that should be mixed in order to produce a mixture having a minimum cost per bag. What is the minimum cost of the mixture per bag?