The network given was the original schedule for project ABC.

$\backslash$table$[[$Act$,\backslash$table$[[$No$.$ of$],[$Days$],[$worked$]],\backslash$table$[[$Remaining$],[$Duration$]]],[$A$,12,3],[$B$,4,0],[$C$,9,0],[$D$,0,7],[$E$,3,0],[$F$,7,0],[$G$,0,2],[$H$,0,3],[$I$,0,4],[$J$,0,5],[$K$,0,1],[$L$,0,2],[M,0,3],[$N$,1,0],[$O$,0,8]]$

After $12$ workdays the project status was described by the data in the Table. Update the CPM network to answer the following questions:

The LF for activity $D$ is:

$21$

$20$

$23$

None of the above

$18$

$19$

$22$

$24$