Question 65

The current erection cost of the structure is $\text{Rs. } 13{,}200$.

1. Effect of daily wage increase:
   The labour wages per day increase by $\dfrac{1}{5}$ of current wages, scaling the wage component by:

   $$1 + \dfrac{1}{5} = \dfrac{6}{5}$$

2. Effect of working period reduction:
   The working hours (time period required) decrease by $\dfrac{1}{24}$ of the current period, scaling the duration component by:

   $$1 - \dfrac{1}{24} = \dfrac{23}{24}$$

3. Compute the new total erection cost:

   $$\text{New Cost} = \text{Current Cost} \times \left(1 + \dfrac{1}{5}\right) \times \left(1 - \dfrac{1}{24}\right)$$
   $$\text{New Cost} = 13{,}200 \times \dfrac{6}{5} \times \dfrac{23}{24}$$

   Notice that $\dfrac{6}{24} = \dfrac{1}{4}$:

   $$\text{New Cost} = 13{,}200 \times \dfrac{23}{5 \times 4} = 13{,}200 \times \dfrac{23}{20}$$
   $$\text{New Cost} = 660 \times 23 = 15{,}180\text{ Rs.}$$

Therefore, the new erection cost is Rs. 15,180, which corresponds to option (B).