Inventory management from Donald Waters pg 75 .

#1
I want to know how did he calculate the holding cost for EOQ model.
Ques.:-
Sarah Brown works for a manufacturer that makes parts for marine engines.
The parts are made in batches, and every time a new batch is started it costs
£1,640 for disruption and lost production and £280 in wages for the fitters.
One item has an annual demand of 1,250 units with a selling price of £300, 60
per cent of which is direct material and production costs. If the company looks
for a return of 20 per cent a year on capital, what is the optimal batch size for
the item and the associated costs?