<?php
$capacities = array(25,150,5000);
foreach ($capacities as $c) {
echo sprintf("Capacity of %s will be allowed to overdraw by %s.\n", $c, log($c)*4);
}
Capacity of 25 will be allowed to overdraw by 12.875503299473.
Capacity of 150 will be allowed to overdraw by 20.042541176385.
Capacity of 5000 will be allowed to overdraw by 34.068772765665.