Could you please re-phrase your question specifically so that you include the actual goal of what you are trying to answer?
In a corporation customers arrive according to a Poisson distribution with mean 35 per hour.
The service time per customer is exponential with mean of 0,035 per hour.
assuming that the system can accommodate a maximum of 30 clients simultaneously.
Many tellers should have the corporation, not to have, in the waiting line,
customers waiting more than 3?