A task has an optimistic completion time of 4 days, a most likely time of 10 days, and a pessimistic time of 13 days. The expected task duration is:

9.5 days

Explanation:

The following can be deduced from the question:

Optimistic Time (To) = 4 days

Most likely Time (Tm) = 10 days

Pessimistic Time (Tp) = 13 days

Expected Task Duration (Te) will then be calculated as:

= (To + 4Tm + Tp) / 6

= (4 + 4×10 + 13) / 6

= (4 + 40 + 13)/6

= 57 / 6

= 9.5 days