$1)$ Interpret the reduced costs for the products that are not currently included in the optimal production plan.

$2)$ Another part of the corporation wants to take $35$ hours of time on test device $3.$ How does this affect the optimal solution?

$3)$ The company has the opportunity to obtain $20$ additional hours on test device $1$ at a cost of $$25$ per hour. Would this be worthwhile?

$4)$ The company has the opportunity to give up $20$ hours of time on device $1$ and obtain $40$ hours of time on device $2$ in return. Would this be worthwhile? Justify your answer.