Solution
Electric field at a point 18 m from the centre of the sphere =$ E_1$
Distance of the point from the centre , $d= 18\;cm =0.18\;m$
$E_1= \large\frac{1}{4 \pi \in_0}. \frac{q}{d^2}$
$\qquad= \large\frac{9 \times 10^9 \times 1.6 \times 10^{-7}}{(1.8 \times 10^{-2})^2}$
$\qquad= 4.4 \times 10^4 \;NC^{-1}$
Therefore, the electric field at a point 18 cm from the centre of the sphere is $4.4 \times 10^4 NC ^{-1}$