Mat for a room: A room is 15 ft by 12 ft. A mat is placed leaving a uniform 1.5 ft margin from each wall. Find the cost of the mat at Rs 3.50 per square foot.

Introduction / Context:
This problem combines inner rectangle dimensions after margins with unit rate multiplication for cost.

Given Data / Assumptions:

• Outer room: 15 ft by 12 ft
• Uniform margin: 1.5 ft on all sides
• Rate = Rs 3.50 per sq ft

Concept / Approach:
Inner mat dimensions subtract twice the margin from each side. Area = length * breadth. Cost = area * rate.

Step-by-Step Solution:

Verification / Alternative check:
3.5 * 100 = 350; 3.5 * 8 = 28; total 378. Correct.

Why Other Options Are Wrong:
472.5, 496, 630, 315 do not match the exact computation 108 * 3.5.

Common Pitfalls:
Subtracting margin only once, or applying it to area directly rather than dimensions first.

Final Answer:
378