$3.$ A company has three warehouses that supply four stores with a given product. Each warehouse has $40$ units of the product. Stores $1,2,3,$ and $4$ require $25,30,35,$ and $30$ units of the product, respectively. a$.)$ Use the Transportation method $($including Northwest$-$corner IFS and MODI$)$ to solve the problem. Clearly mark all steps, Ri$,$ Ki values, and opportunity costs of unoccupied cells. For each improvement step, write down the arrows, signs, and determination of minimum capacity. b$.)$ Form an LP problem and solve it in an Excel solver. Verify that the results are the same as the results you obtained from the transportation method. $4$c Store

$2-5$ Warehouse $1234$

$15465$

$23644$

$34332$