What is the current optimal solution and the objective function value?

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

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

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

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

What is the sensitivity range for the objective function coefficient of decision variable $2($operation days of mill $2)?$

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

Which constrains are binding?

If we can decrease the demand of high$-$grade aluminum by $2$ tons at the cost of $$\frac{1000}{?}$ ton, is it worth doing this? And why?

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

If we can purchase $2$ tons of medium$-$grade aluminum from our competitors at $$\frac{2000}{?}$ ton to satisfy part of the demand, instead of making it in our mills $($in other words, we can decrease the demand by $2$ tons at the price of $$\frac{2000}{?}$ ton$),$ is it worth doing this? And why?

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

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