Use Johnson's rule to determine the optimal sequencing for the seven jobs to be processed on$...$

Question:

$1.)$ Use Johnson's rule to determine the optimal sequencing for the five jobs to be processed on two machines in a fixed order $($Machine $1$ before Machine

$2).$ The processing times in hours are given in the table below.

a$.$ What is the optimal sequence?

b$.$ What is the total flow time for this sequence? c$.$ which job is first to be scheduled? is it scheduled to be the first job or the last? explain.

Job Machine $1$ Machine $2$

A $1011$

B $817$

C $1410$

D $137$

E $108$

F $259$

G $615$