Products X and Y are to be blended to produce a mixture that is at least 30% A and 30% B, and contain x + y gallons. Product X is 50% A and 40% B and costs $10 per gallon; Product Y is 20% A and 10% B and costs $2 per gallon. Formulate a linear programming model that can be used to determine the optimal amount of each product blended in producing the required mixture (final product) at a minimum cost. Please note that this question requires only model formulation