Stadium Construction Project Problem: What is the combined slack for actbities

$\backslash$table$[[$ACTIVITY IMMEDIATE PREDECESSOR DURATION $($daye$),,],[$A$,$A$,1],[$B$,$A$,4],[$C$,$A$,3],[$D$,$B$,7],[$E$,$C$,$D$,6],[$F$,$E$,$F$,2],[$G$,$D$,7],[$H$,$G$,$H$,],[$I$,9,]]$

$2$

$0$

$1$

$4$

$3$