AB 1 1 Quot Marsh and Root Construction have won the contract to widen and resurface a section of road The site manager has identified the following tasks together with the tasks that must precede them and their anticipated durations: Activity Description Precedence Optimistic Most Pessimistic Likely Relocate bus stop 1 2 3 B Install temp traffic lights 1 1 2 C Install safety berries 1 1 D Plane road 2 4 Lift Kerbstones 2 3 6 F Replace ironworks D 1 3 7 G Lay and roll tarmac F 1 1 1 H Replace Kerbstones E 3 4 1 Road painting G 2 2 3 J Remove safety barriers 1 1 1 2 K Remove temp traffic light: J 1 1 L Restore bus stop H 2 2 4 9 1 NI a) Calculate mean for each activity b) Use mean time to calculate critical path. c) Calculate standard deviation for the whole project time