jobs A$,$ B$,$ and C are in queue at work center $10$ before being completed on work center $20.$ The following information pertains to the jobs and the work centers: $($Job$,$ Process time $($day$)$ at WC $10,$ process time $($day$)$ at WC $20,$ Due Date$)$: $($A$,8,6,24)$; $($B$,6,4,20)$; and $($C$,5,2,22).$ For this problem, there is no move time between two centers. Today is day $1.$ If the jobs are scheduled by shortest process time $($SPT$)$ rule today, how many idle days from day $1$ to the day end $($the date that last job is completed$)$ in work center $20$ will have?

Group of answer choices

none of them

$13$

$12$

$15$

$14$