<?php
    function getPayment($percent, $comission, $basicPayout, $credit, $payout) {
        $payment = $basicPayout;
 
        while ($credit > 0) {
            $credit = $credit * (1 + $percent) + $comission - $payout;
 
            if ($credit <= $payout) {
                $payment += $credit;
 
                return round($payment, 2);
            } else {
                $payment += $payout;
            }
        }
    }
 
 
    $credit = 39999;
    $payout = 5000;
    $banks = array('HomoCredit' => getPayment(0.04, 500, 0, $credit, $payout),
                   'SoftBank' => getPayment(0.03, 1000, 0, $credit, $payout),
                   'StrawBerry' => getPayment(0.02, 0, 7777, $credit, $payout));
 
 
    foreach($banks as $bankName => $payment) {
        echo "Плата у $bankName: $payment руб.\n";
    }
 
    $cheapestPayment = min(array_values($banks));
    echo "\nНаиболее дешёвая цена ".$cheapestPayment.' руб. в банке '.array_search($cheapestPayment, $banks).'!';
?>

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