Conditional Formatting Analysis of Rates (20% above and 20% below the average)

Hi,

Forgive, this seems very basic.

I have 4 companies who have priced the same items. I now have to do a rate analysis.

I am trying to conditional format;
any rates 20% above the average 'red'
any rates 20% below the average 'green'


Cheers for any help on this.