$($ii$)$ consider the marginal value$($shadow price$)$ of an additional hour of cutting capacity $.$ over what range of cutting capacity is this value valid?$($iii$)$ if the amount of spruce available to the firm from decreases $160$ to $100$ pounds, will it affect the optimal solution or the optimal value of the objective function $?$ why or why not? if yes then what would the new value be$?$