The Jean-Pierre Amor Company manufactures two lines of designer yard gates, called model A and model B. every gate requires blending a certain amount of steel and zinc; the company has available a total of 25000 lb of steel and 6000 lb of zinc. Each model A gate requries a mixture of 125 lb of steel and 20 lb of zinc, and each yields a profit of $90. Each model B gate requires 100 lb of steel and 30 lb of zinc and can be sold for a profit of $70. (Formulate only) use constraints