Consider Q$2|$ prmp $|$ Cmax with the jobs

jobs $1234$

pj $36241612$

and machine speeds v$1=2$ and v$2=1.$

$($a$)$ Find the makespan under LRPT when preemptions can only be made

at the time points $0,4,8,12,$ and so on$.$

$($b$)$ Find the makespan under LRPT when preemptions can only be made

at the time points $0,2,4,6,8,10,12,$ and so on$.$

$($c$)$ Find the makespan under LRPT when preemptions can be made at any

time.

$($d$)$ Compare the makespans under $($a$),($b$),$ and $($c$).$