A diet is to contain atleast 80 units of vitamin A and 100 units of minerals . Two foods ` F_(1)" and " F_(2)` are available . Food ` F_(1)` costs Rs 4 per unit and food ` F_(2)` costs Rs 6 per unit . One units of food ` F_(1)` contains at 3 units of vitamin A and 4 units of minerals . One unit of food ` F_(2)` contains 6 units of vitamin A and 3 units of minerals . Formulate this as a linear programming problem . find the minimum cost for diet that consists of mixture of these two foods and also meets the minimal nutritional requirements .