Lifecycle Question:

Hi Sir, I have a question that I cannot seem to understand: Company B is about to begin developing a new product for launch in its existing market. They have forecast sales of 20,000 units and the marketing department suggest a selling price of $43./unit. The company is seeking to make a mark-up of 40% product cost. It is estimated that the lifetime costs of the products wil be as follows: 1) design and development costs $43,000 2) Manufacturing costs $15/unit 3) Plant decommissioning costs $30,000 The company estimates that if it were to spend an additional $15000 on design, manufacturing costs/unit could be reduced? What is the life cycle cost? Answer: Original life cycle cost per unit = (43,000+(20,000 x $15) + 30,000)/15,000 = $24.87 My question is why do we have to divide by the 15,000? I do not see the rationale behind this. Could you please explain. Kind regards, Yazan