Consider the following work breakdown structure:

$\backslash$table$[[,$Duration Estimates $($Days$)],[$Activity$,$Precedes,Optimistic,Most Likely Pess,$],[$Start$,$U$,$V$,-,-,-],[$U$,$W$,35,50,65],[$V$,$W$,$X$,28,40,52],[$W$,$Z$,26,35,44],[$X$,$Y$,28,40,52],[$Y$,$Z$,26,29,38],[$Z$,$End,$36,60,84]]$

What is the estimated expected $($mean$)$ time for activity Y$?$