QUESTION $31$

Consider the following work breakdown structure:

$\backslash$table$[[,\backslash$table$[[$Start$],[$Activity$]],\backslash$table$[[$Finish$],[$Node$]],$Duration Estimate $($Days$)],[$A$,1,2,9,15,21],[$B$,1,3,13,21,23],[$C$,2,4,6,9,18],[$D$,2,5,23,35,47],[$E$,3,5,19,26,27],[$F$,4,6,23,29,41],[$G$,5,6,14,20,26],[$H$,6,7,2,5,8]]$

What is the probability that the critical path for this project will be completed within $75$ weeks? $($Please use decimal point format.$)$