<?php
$capacities = array(25,150,50000,200000,5000000);
foreach ($capacities as $c) {
echo sprintf("Capacity of %s will be allowed to overdraw by %s.\n", $c, log($c,2));
}
Capacity of 25 will be allowed to overdraw by 4.6438561897747.
Capacity of 150 will be allowed to overdraw by 7.2288186904959.
Capacity of 50000 will be allowed to overdraw by 15.609640474437.
Capacity of 200000 will be allowed to overdraw by 17.609640474437.
Capacity of 5000000 will be allowed to overdraw by 22.253496664212.