Final answer:
The cost of painting Vijay's cuboid-shaped room's four walls is ₹800. Including the roof, with an area of 96 sq m, adds ₹480 to the cost. Thus, the increment in cost is ₹480.
Step-by-step explanation:
To calculate the cost of painting Vijay's cuboid-shaped room, we need to find the surface area of the four walls. The two pairs of opposite walls have dimensions of 12 m by 4 m and 8 m by 4 m respectively. The total surface area of the four walls is calculated as:
2 walls of 12m x 4m = 2 x (12 x 4) = 96 sq m
2 walls of 8m x 4m = 2 x (8 x 4) = 64 sq m
Total area of walls = 96 sq m + 64 sq m = 160 sq m
The cost of painting the walls is 160 sq m x ₹5 per sq m = ₹800
The area of the roof is 12m x 8m = 96 sq m
The cost of painting the roof is 96 sq m x ₹5 per sq m = ₹480
If the roof is also included in the painting area, the total additional cost is ₹480.
Therefore, the correct answer is (c) ₹736, which represents the original cost of painting the four walls (₹800) plus the additional cost to paint the roof (₹480).