On average, 10 customers are expected to be processed or served at a salon every hour, of which 66.67% receive haircut and rest receive hair coloring service. Given that only a few standard styling options are offered, it is estimated that: Customers who request haircut will spend, on average, a total of 27 minutes in the salon, whereas customers who request hair coloring will spend, on average, a total of 36 minutes in the salon. What is the average number of customers in the hair salon at any given instance? (Please enter the numeric value below)