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Question $9$

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Sydney Manufacturing produces custom$-$built pollution control devices fro medium$-$size steel mills. The most recent project undertaken by the manager requires $6$ different activities. The appropriate data is shown in the following $($a$=$Optimistic, m$=$most likely, b$=$ pessimistic times$).$ Assume that the activity times are independent:

Activity

Immediate predecessors$($s$)$

a

m

b

A

$-$

$2$

$4$

$6$

B

$-$

$1$

$2$

$3$

C

$-$

$6$

$6$

$6$

D

A$,$B

$5$

$8$

$11$

E

C

$1$

$9$

$17$

F

D$,$E

$2$

$3$

$4$

a$)$ Determine the total expected project completion time.

b$)$ How much is the Variance of the project?

Select one:

a$)13$ days; b$)4\mathrm{.}43$

a$)18$ days; b$)7\mathrm{.}22$

a$)13$ days; b$)3\mathrm{.}55$

a$)18$ days; b$)6\mathrm{.}5$