Slick Oil Company has $3$ warehouses from which it can ship to $4$ retailers. The monthly demand at retailer $1$ is $350$ drums, at retailer $2$ it is $100,$ at retailer $3$ it is $50$ and at retailer $4$ it is $150$ drums. Warehouse $1$ has an inventory of $250$ units, Warehouse $2$ has an inventory of $150$ units, and Warehouse $3$ has an inventory of $300$ units. Given the costs below, they need to determine how product should be shipped between the warehouses anid the retailers.