$26.$ Consider the example presented in Section $8\mathrm{.}2$ of scheduling the production of the valve casing assembly. a$.$ Suppose that the production capacity in any week is $100$ valve casings. Using the algorithm presented in this section, determine the planned order release for the valve casings. b$.$ What gross requirements schedule for the valves does the lot sizing you obtained in part $($a$)$ give? c$.$ Suppose that the production capacity for the valves is $200$ valves per week. Is the gross requirements schedule from part $($b$)$ feasible? If not, suggest a modification in the planned order release computed in part $($a$)$ that would result in a feasible gross requirements schedule for the valves. $\backslash$begin$\{$tabular$\}\{$lrrrrrrrrrr$\}\backslash$hline Week & $4$ & $5$ & $6$ & $7$ & $8$ & $9$ & $10$ & $11$ & $12$ & $13\backslash \backslash$ Time$-$phased net requirements & $42$ & $42$ & $32$ & $12$ & $26$ & $112$ & $45$ & $14$ & $76$ & $38\backslash \backslash \backslash$hline $\backslash$end$\{$tabular$\}$