Suppose we have the following activity list that includes information on immediate predecessors along activity completion times $($in weeks$)$ under optimistic, normal, and pessimistic scenarios:

Immediate

Activities Predecessor Optimistic Normal Pessimistic

A $---1711$

B $---3810$

C A$,$B $111$

Using this information, what is the variance of Activity B$?$

Question $8$ options:

$0$

$1\mathrm{.}36$

$2\mathrm{.}78$

$1\mathrm{.}00$