$($a$)$ Formulate this model in AMPL, and solve the following instance. There are T $=13$ periods, l $=8$

production lines, and a maximum change of M $=3$ crews per period. The products are $18$REG,

$24$REG, and $24$PRO, with production rates r p of $1\mathrm{.}194,1\mathrm{.}509$ and $1\mathrm{.}509$ respectively. Crews work

either a day shift with wages ws of $$44,900,$ or a night shift with wages $$123,100.$ The demands

and working hours are given as follows by period: