Two foods contain only proteins, carbohydrates, and fats. Food A costs $1 per pound and contains 30%

Question:

Two foods contain only proteins, carbohydrates, and fats. Food A costs $1 per pound and contains 30% protein and 50% carbohydrates. Food B costs $1.50 per pound and contains 20% protein and 75% carbohydrates. What combination of these two foods provides at least 1 pound of protein, 2 1/2 pounds of carbohydrates, and 1/4 pound of fat at the lowest cost?