A vacuum manufacturer calculated the cost per unit for one vacuum to be $149. This was calculated by adding together April's direct labour, direct materials, and manufacturing overhead and dividing by the total units produced during April, which was 5,000. There was no beginning or ending inventories. In May, they plan to manufacture 4,500 units. What would happen to May's cost per unit? Select one: a. We can't calculate the direction of change in the unit costs. b. The cost per unit will go down c. The cost per unit will stay the same d. The cost per unit will go up