$12\mathrm{.}7$ William Beville's computer training school, in Richmond, stocks workbooks with the following characteristics:

Demand $D=19,500$ units$/$year

Ordering cost

$)/()$ order

Holding cost $H=$$$\frac{4}{?}$

$$ unit$/$year

a$)$ Calculate the EOQ for the workbooks.

b$)$ What are the annual holding costs for the workbooks?

c$)$ What are the annual ordering costs?