Set up the following linear programming problem (do not solve it): Moonshine Nucky is trying to give back to the community. He plans to establish a Food & Roof Foundation to help the less fortunate. Building the Foundation's main building requires 500 tons of timber and 900 tons of stone. Two companies in the area supply timber and stone. Company A charges $5/ton for timber and $4/ton for stone and a minimum of 200 tons of material must be ordered. Company B charges $6/ton for timber and $2/ton for stone and a minimum of 250 tons of material must be ordered. How many tons of timber and how many tons of stone must Nucky order from each company to minimize the total material cost?

The answer is in the book, but please provide an explanation to every function / inequality in the system.