Consider a $$PERT$$ network for a project involving six tasks ($$a$$ to $$f$$)

The standard deviation of the critical path of the project is

A project has six activities $$(A$$ to $$F)$$ with respective activity durations $$7,5,6,6,8,4$$ days. The network has three paths $$A-B,C-D$$ and $$E-F.$$ All the activities can be crashed with the same crash cost per day. The number of activities that need to be crashed to reduce the project duration by $$1$$ day is

A project consists of activities $$A$$ to $$M$$ shown in the net in the following figure with the duration of the activities marked in days.

The project can be completed

A project consists of three parallel paths with mean durations and variances of $$(10,4), (12,4)$$ and $$(12,9)$$ respectively. According to the standard $$PERT$$ assumptions, the distribution of the project duration is