A spherical conductor of radius 10 cm has a charge of 3.2 × 10^–7 C distributed uniformly. What is the magnitude of electric field at a point 15 cm from the centre of the sphere?

(1/4π∈₀ = 9 x 10⁹ Nm²/C²)

(1) 1.28 × 10⁵ N/C

(2) 1.28 × 10⁶ N/C

(3) 1.28 × 10⁷ N/C

(4) 1.28 × 10⁴ N/C