Inverse Proportion: Illumination and Distance Squared

The illumination, \(I\) units, of a bulb varies inversely as the square of the distance, \(d\) metres.

Given that the illumination is \(9\) units when the distance is \(2\) m,

1. express \(I\) in terms of \(d\),
2. find the percentage change in illumination when the distance from the bulb is reduced to \(\frac{1}{5}\) of its original value.