At a Sales Volume of 36,000 Units, Quale Corporation's Sales

At a sales volume of 36,000 units, Quale Corporation's sales commissions (a cost that is variable with respect to sales volume) total $187,200.
-To the nearest whole cent, what should be the average sales commission per unit at a sales volume of 36,400 units? (Assume that this sales volume is within the relevant range.)

A) $5.20
B) $4.89
C) $5.17
D) $5.14