Given
Inner dimensions of wooden box are 2 m by 1.2 m by 0.75 m
Thickness of the wood = 2.5 cm = 2.5/100 m = 0.025 m
Now
External dimensions of wooden box are
= (2 + 2 x 0.025) by (1.2 + 2 x 0.025) by (0.75 + 2 x 0.025)
= (2+0.05) by (1.2+0.05) by (0.75+0.5)
= 2.05 by 1.25 by 0.80
Thus
Volume of solid = External volume of box - Internal volume of box
= 2.05 x 1.25 x 0.80 m3 − 2 x 1.2 x 0.75 m3
= 2.05 − 1.80 = 0.25 m3
Given, the cost of wood = Rs 5400 for 1 m3
Hence, Total cost = Rs 5400 x 0.25 = Rs 5400 x 25/100 = Rs 54 x 25
= Rs 1350