Additional Algo $5-1$ Demand with Mixed Products

A printing shop with three processes $($binding$,$ photocopy, and checkout$)$ has two types of customers $($copy only and copy and bind$).$ A printing shop has a demand of $9$ copy only customers per hour and $4$ copy and bind customers per hour. Photocopy customers visit the photocopy and checkout processes while copy and bind customers visit all three processes.

What is the total demand at the checkout process each hour?

Total demand of customer's per hour