Normal Company Pays a Sales Commission of 4% on Each

Normal Company pays a sales commission of 4% on each unit sold. If a graph is prepared, with the vertical axis representing per-unit cost and the horizontal axis representing units sold, how would a line that depicts sales commissions be drawn?

A) As a straight diagonal line, sloping upward to the right.
B) As a straight diagonal line, sloping downward to the right.
C) As a horizontal line.
D) As a vertical line.
E) As a curvilinear line.