Due to Increased Sales, a Company Is Considering Building Three

Due to increased sales, a company is considering building three new distribution centers (DCs) to serve four regional sales areas. The annual cost to operate DC 1 is $500 (in thousands of dollars). The cost to operate DC 2 is $600 (in thousands of dollars.). The cost to operate DC 3 is $525 (in thousands of dollars). Assume that the variable cost of operating at each location is the same, and therefore not a consideration in making the location decision.
The table below shows the cost ($ per item) for shipping from each DC to each region.
Region
$$\begin{array} { | c | c | c | c | c | } \hline \mathrm { DC } & \mathrm { A } & \mathrm { B } & \mathrm { C } & \mathrm { D } \\\hline 1 & 1 & 3 & 3 & 2 \\\hline 2 & 2 & 4 & 1 & 3 \\\hline 3 & 3 & 2 & 2 & 3 \\\hline\end{array}$$
The demand for region A is 70,000 units; for region B, 100,000 units; for region C, 50,000 units; and for region D, 80,000 units. Assume that the minimum capacity for the distribution center will be 500,000 units.
Write the constraints for the 3 distribution centers.