At a sales volume of 34,500 units, Thoma Corporation's sales commissions (a cost that is variable with respect to sales volume) total $455,400.
To the nearest whole cent, what should be the average sales commission per unit at a sales volume of 48,200 units? (Assume that this sales volume is within the relevant range.)
$12.57
$13.20
$13.89
$12.89