18) C

Surface area of original marble chip = 6 x 1 x 1 = 6 cm²
Surface area of a single powder cube = 6 x 0.01cm x 0.01cm = 0.0006 cm²
Volume of original cube = 1 cm³
Volume of powder cube = 0.01 x 0.01 x 0.01 = 0.000001 cm³

Number of powder cubes = 1cm³ ÷ 0.000001cm³ = 10⁶ cubes
Total surface area of powder cubes = 10⁶ x 0.0006cm² = 600 cm²
Extra surface area = 600 – 6 = 594 cm²

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