I have a car wash where on Saturdays the number of cars that arrive increases, the cars arrive on average (one) every 12 minutes. It takes a person to wash a car completely 20 minutes. The waiting cost per car per hour is estimated at 150 pesos and I pay each car wash employee 50 pesos per hour. The problem is to decide what is the number of people that I should have in my carwash on Saturdays to minimize the total cost of the system, and what is this minimum total cost?

Please solve clearly.