<?php
$capacities = array(50000,200000,5000000);
foreach ($capacities as $c) {
echo sprintf("Capacity of %s will be allowed to overdraw by %s.\n", $c, log($c*10));
}
Capacity of 50000 will be allowed to overdraw by 13.122363377404.
Capacity of 200000 will be allowed to overdraw by 14.508657738524.
Capacity of 5000000 will be allowed to overdraw by 17.727533563392.