Which one of the following is represented by D/Q in the above expression?

Question

For economic manufacture, the total annual cost is given as 12 M $\left ( P+\frac{D}{Q} \right )$  ; where

         M is number of parts made per month

         P is processing cost per part

         Which one of the following is represented by D/Q in the above expression?

         (a) Setting up cost

         (b) Profit per part

         (c) Bonus

         (d) Setting up cost/part