Consider the following operations:
1. Drilling
2. Blasting
3. Mucking
4. Placing steel
5. Placing concrete
The correct sequence of these operations in tunnel construction is

The normal time required for the completion of project in the above problem is

A. 9 days

B. 13 days

C. 14 days

D. 19 days

If t_o, t_p and t_m are the optimistic, pessimistic and most likely time estimates of an activity respectively, the expected time t of the activity will be

A. $$\frac{{{{\text{t}}_{\text{o}}} + 3{{\text{t}}_{\text{m}}} + {{\text{t}}_{\text{p}}}}}{2}$$

B. $$\frac{{{{\text{t}}_{\text{o}}} + 3{{\text{t}}_{\text{m}}} + {{\text{t}}_{\text{p}}}}}{3}$$

C. $$\frac{{{{\text{t}}_{\text{o}}} + 4{{\text{t}}_{\text{m}}} + {{\text{t}}_{\text{p}}}}}{4}$$

D. $$\frac{{{{\text{t}}_{\text{o}}} + 4{{\text{t}}_{\text{m}}} + {{\text{t}}_{\text{p}}}}}{5}$$

E. $$\frac{{{{\text{t}}_{\text{o}}} + 4{{\text{t}}_{\text{m}}} + {{\text{t}}_{\text{p}}}}}{6}$$

A construction schedule is prepared after collecting

A. Number of operations

B. Output of labour

C. Output of machinery

D. All the above

If an activity has its optimistic, most likely and pessimistic times as 2, 3 and 7 respectively, then its expected time and variance are respectively

A. 3.5 and $$\frac{5}{6}$$

B. 5 and $$\frac{{25}}{{36}}$$

C. 3.5 and $$\frac{{25}}{{36}}$$

D. 4 and $$\frac{5}{6}$$