ET$459$ Class exercise $2$: find the critical path and duration of the following project.

$\backslash$table$[[$Activity$,$Predecessors,Normal Duration $($weeks$)],[$A$,-,6],[$B$,$A$,10],[$C$,$A$,8],[$D$,$B$,12],[$E$,$B$,$C$,10],[$F$,$C$,14],[$G$,$D$,$ C$,7],[$H$,$E$,$F$,9],[$I$,$G$,$H$,6],[$J$,$I,$5],[$K$,$I,$6],[$L$,$J$,$ K$,8],[$M$,$I, K$,8],[$N$,$J$,$ K$,6],[$O$,$L$,$ M$,$ N$,7],[$P$,$O$,6]]$