$2\mathrm{.}3.$ Consider the instance of $1||{\displaystyle \underset{?}{\overset{?}{}}}{U}_j$ with the following processing times and due dates.

$\backslash$table$[[$jobs$,1,2,3,4],[p_j,7,6,4,8],[d_j,8,9,11,14]]$

$($a$)$ Find all optimal sequences and compute the value of the objective.

$($b$)$ Formulate a generic rule based on the due dates and processing times which yields an optimal sequence for any instance.