Consider the following work breakdown structure:

Time Estimates $($days$)$

$\backslash$table$[[$Activity$,$Precedes,Optimistic,Most Likely,Pessimistic$],[$Start$,$A$,$ B$,$ C$,-,-,-],[$A$,$D$,38,50,62],[$B$,$E$,90,99,108],[$C$,$End,$85,100,115],[$D$,$F$,19,25,31],[$E$,$End,$91,100,115],[$F$,$End,$62,65,68]]$

What is the estimated slack time for activity A$?$

$0$ days

$20$ days

$100$ days

$40$ days

$60$ days