Prison Current Level

function getLevelByRating(int $rating): float
{
    $numbers = [
        'a' => 9.006734007,
        'b' => 12.03703704,
        'c' => -21.04377104 - $rating
    ];
    return (-$numbers['b'] + sqrt(pow($numbers['b'], 2) - 4 * $numbers['a'] * $numbers['c'])) / (2 * $numbers['a']) + 0.00001;
}