Following table gives the activity time estimates for an activity in project.

$\backslash$table$[[$Activity$,\backslash$table$[[$Optimistic Time$],[($hours$)]],\backslash$table$[[$Most Likely Time$],[($hours$)]],\backslash$table$[[$Pessimistic Time$],[($hours$)]]],[\backslash$table$[[$Printing the$],[$Invitation cards$]],2,2\mathrm{.}5,6]]$

a$.$ What is the expected activity duration $(t_e)$ for the activity?

b$.$ What is the variance of activity $({}^2)?$