Georgia-Pacific currently is timbering two sites (T1 and T2) to obtain its lumber stock. The timber is shipped to either of two lumber storage yards (Y1 and Y2). When needed, it then is shipped on to the company's mill (M). The diagram below depicts this distribution network. The diagram also shows the monthly amounts produced at the timber sites and needed at the mill, as well as the shipping cost and the maximum amount that can be shipped per month through each shipping lane. 60 tons T1 $800/ton produced 30 tons max. Y1 $1,200/ton $400/ton 30 tons max. 60 tons max. 100 tons $900/ton M 40 tons max. needed $800/ton 40 tons T2 $700/ton 80 tons max. produced 40 tons max. Y2 Management wants to determine the most economical plan for shipping the timber from the timber sites through the distribution networks to the plant. a. Identify all the requirements that will need to be expressed in fixed-requirement constraints. (5 pts) b. Express the model in algebraic form. (15 pts) C. Formulate and solve a linear programing model for this problem on a spreadsheet. (15 pts)