Plastering a rectangular tank (inside walls + bottom):\nA tank is 25 m long, 12 m wide, 6 m deep. Find cost of plastering its walls and bottom at Rs 0.75 per sq. m.

Introduction / Context:
Compute interior area to be plastered (four walls + bottom) and multiply by the given rate.

Given Data / Assumptions:

• Length L = 25 m, width W = 12 m, depth H = 6 m.
• Rate = Rs 0.75 per m^2.

Concept / Approach:
Area to plaster = bottom + all four interior walls.

Step-by-Step Solution:

Verification / Alternative check:
Unit-check: m^2 * Rs/m^2 ⇒ Rs — consistent.

Why Other Options Are Wrong:
Other totals correspond to incorrect wall counts or missing the bottom.

Common Pitfalls:
Including the top (open tank), or double-counting a pair of walls.

Final Answer:
Rs. 558