The current erection cost of a structure is Rs. 13,200. If the labour wages per day increase by 1/5 of the current wages and the working hours decrease by 1/24 of the current period, then the new cost of erection in Rs. is

Let ‘W’ be the labour wages and ‘T’ be the working hours. Now, total cost is a function of W × T. Increase in wages = 20% $\therefore$ Revised wages = 1.2 W Decrease in labour time = $\left( \dfrac{100}{24}\% \right)$ $\therefore$Revised time = $\left( 1- \dfrac{1}{24}\right)T = \dfrac{23}{24}T$ $\therefore$Revised total cost = 1.2 $\times \dfrac{23}{24}$WT = 1.15 × WT                                     = 1.15 × 13200 = 15,180