Consider the following work breakdown structure:

$\backslash$table$[[,$Start,Finish,Duration $($days$)],[$Activity$,$Node,Node,Optimistic,Most Likely,Pessimistic$],[$A$,1,2,41,50,59],[$B$,1,3,54,60,66],[$C$,2,4,58,70,82],[$D$,3,4,32,41,44]]$

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

Multiple Choice

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$79$ days

$20$ days

$$

$19$ days