An imaginary spherical surface has radius 1.5 m. Fully contained within and concentric with the spherical surface is a spherical conductor with a uniform surface charge density of 1.5 × 10^{-7} C/m^{2}. What is its radius if the flux through the imaginary surface is 480 Nm^{2}/C?

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3.2 cm

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4.7 cm

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9.5 cm

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6.4 cm

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3.9 cm