Step 1: Convert all units to meters

The length and breadth are already in meters, but the height is given in centimeters. Convert height to meters: $h = 90\text{ cm} = \frac{90}{100}\text{ m} = 0.9\text{ m}$.

$h = 0.9\text{ m}$

Step 2: Find the Total Surface Area of the Cuboid

Since the box is closed, use the total surface area formula for a cuboid: $\text{TSA} = 2(lb + bh + hl)$.

$\text{TSA} = 2(2.5 \times 2 + 2 \times 0.9 + 0.9 \times 2.5)$

Step 3: Evaluate TSA

Calculate each product inside the parentheses: $2.5 \times 2 = 5$, $2 \times 0.9 = 1.8$, and $0.9 \times 2.5 = 2.25$. Sum them up: $5 + 1.8 + 2.25 = 9.05$. Multiply by $2$: $\text{TSA} = 2 \times 9.05 = 18.1\text{ m}^2$.

$\text{TSA} = 18.1\text{ m}^2$

Step 4: Calculate the Total Cost of the Canvas

Multiply the total surface area by the cost per square meter: $\text{Cost} = 18.1 \times 70 = 1267\text{ ₹}$.

$\text{Cost} = ₹1,267$