Explaination
The $20,000 donation is to be shared between Pete and Mike in the ratio proportionate to their investments, which is 4 is to 1.
Pete's counterpart will be represented as 4/5, while Mike's counterpart will be 1/5, making a whole of 5/5.
Computing for Mike's counterpart to the total donation of $20,000:
$20,000 x $7990_w9_h37.png$ = $4,000