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

A. 9 days B. 13 days C. 14 days D. 19 days

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. Number of operations B. Output of labour C. Output of machinery D. All the above

A. 3.5 and $$\frac{5}{6}$$ B. 5 and $$\frac{{25}}{{36}}$$ C. 3.5 and $$\frac{{25}}{{36}}$$ D. 4 and $$\frac{5}{6}$$