The Following Information Is the Basis for the Next Three

The following information is the basis for the next three questions.
Jim and Carol Spalding have a crack in their waterline and need to replace it. This will require digging up the water line, replacing it, filling the hole, leveling the soil, and re-seeding the grass. The Spalding's plumber suggests that, since they have the well dug up, they should replace the foot valve in the well also. Below are the plumber's estimates of the time in hours) necessary to perform each of the activities required.
$$\begin{array} { | c | l | c | c | c | c | } \hline \text { Activity } & \text { Description } & \text { Predeces sor } & \text { Optimistic } & \text { Most Lik ely } & \text { Pessim istic } \\\hline \text { A } & \text { Digging } & - & 2 & 3 & 4 \\\hline \text { B } & \text { Replace line } & \text { A } & 1 & 1.5 & 2 \\\hline \text { C } & \text { Replace foot valve } & \text { B } & .5 & 1 & 1.5 \\\hline \text { D } & \text { Fill hole } & \text { C } & 1.5 & 2 & 5.5 \\\hline \text { E } & \text { Level soil } & \text { D } & .5 & 1 & 1.5 \\\hline \text { F } & \text { Reseed lawn } & \text { E } & .4 & .5 & .6 \\\hline \end{array}$$

-Carol Spalding can't bear to see her lawn all dug up so she has decided to visit her mother on the day the work is to be done. Carol wants to return home at 6:45 p.m., what is the probability the work will be complete when Carol arrives home?

A) 95%
B) 99.3%
C) 99.5%
D) 99.8%
E) 100%