Let the original daily wage rate be W and the total working period (in days/hours) be T.
The initial cost of erection is:
C=W×T=13,200 According to the problem:
New labour wages per day, W′=W+51W=56W
New working hours/period, T′=T−241T=2423T
Therefore, the new cost of erection is:
C′=W′×T′=(56W)×(2423T)=(56×2423)×(W×T) C′=2023×13,200=23×660=15,180 Thus, the new cost of erection is Rs. 15,180, which corresponds to option (B).