The Ace Machine Company is considering using a priority scheduling rule in its fabrication shop and must decide whether to use: the critical ratio rule, the order slack rule, the shortest operation next rule, or the slack per operation rule. The table below shows the company$$s current inventory and shop status.

Order Number

Total Remaining Manufacturing Time

Time Remaining until Due Date

Current Operation Processing Time

$1$

$15$

$12$

$8$

$2$

$12$

$15$

$5$

$3$

$10$

$14$

$4$

$4$

$15$

$18$

$3$

$5$

$20$

$19$

$6$

State the formula for calculating the priority index for each of the sequencing rules given previously.

Compute the scheduling priority for each order in the table, four sequencing rules.