Correct Answer - Option 2 : 600 cm

^{2}
**Given:**

Three solid iron cubes of edges 6 cm, 7 cm, and 8 cm.

71 cm^{3} of the melted material is lost due to improper handling.

**Concept:**

The volume of cube = a^{3}

The total surface area of cube = 6a^{2}

Where a = side

When a figure melted together to make a new figure then the volume is equal.

**Explanation:**

Volume of three solid cube = Volume of a new cube

V = 6^{3} + 7^{3} + 8^{3} = 216 + 343 + 512 = 1071 cm^{3}

(∵ 71 cm^{3} of the melted material is lost due to improper handling)

So volume of new cube (a^{3}) = 1071 - 71 = 1000 cm^{3}

⇒ a = 10 cm

Total surface area of volume = 6a^{2} = 6 × 10^{2}

**∴ The total surface area of new cube is 600 cm**^{2}.