Question $4$

Day's Nail Salon has two technicians available to paint customer's nails. Both technicians provide a similar experience and skill, but technician $2$ is just a littl bit slower than the other. The process flow below shows that all customers go through steps A and B and then can be served at either of the two technicians step C$.$ The process ends after step D$.$ The numbers in parentheses indicate t$)$ minutes it takes that activity to process a customer.

This process can serve customers per hour. $($Enter your response as an integer$).$