$1.$ What is the current optimal solution and the objective function value?

$$

$2.$ What is the objective function coefficient of decision variable $1($operation days of mill $1)?$

$$

$$

$3.$ What is the sensitivity range for the objective function coefficient of decision variable $1($operation days of mill $1)?$

$$

$$

$4.$ If the operation cost of mill $1$ increases from $$6000$ to $$7500,$ will the optimal solution change? And why?

$$

$$

$5.$ What is the objective function coefficient of decision variable $2($operation days of mill $2)?$

$$

$6.$ If the operation cost of mill $2$ decreases from $$7000$ to $$6500,$ will the optimal solution change?

$$

$7.$ Which constrains are binding?

$$

$8.$ If the demand of medium$-$grade aluminum increases by $4$ tons, what is the new total cost?

$9.$ If the customer needs additional $5$ tons of low$-$grade aluminum and is willing to pay $$1000/$ton$,$ do we want to accept this offer? And why?

$$

$10.$ If the customer needs additional $20$ tons of low$-$grade aluminum and is willing to pay $$1000/$ton$,$ do we want to accept this offer? And why?

$$