Installation Schedule

Building A

Can't happen first

Building $B$

Must happen before Building D

Building $C$

Must include the $12$th in the schedule

Building D

Must happen before Building $A$

Question

New security systems must be installed on $4$ buildings, one at a time. Installation takes $4$ days. The installers do not start a new job on Mondays or work weeke which date should the work on Building A begin, to complete all $4$ buildings as early as possible?

Calendar

$\backslash$table$[[$SUN$,$MON,TUE,WED,THU,FRI,SAT$],[,1,2,3,4,5,6],[7,8,9,10,11,12,13],[14,15,16,17,18,19,20],[21,22,23,24,25,26,27],[28,29,30,,,,]]$