A small company just opened a new massage station at the Philadelphia airport. The company has a stand that offers massages to travelers. Customers can select a length of time for a massage between 5 and 20 minutes, and there is a unique rate of $30 independent of the length of time chosen by customers. The average massage length, requested by customers, is 15 minutes with a standard deviation of 10 minutes. There are four employees delivering massages. The average number of potential customers requesting a massage is 20 per hour. The interarrival times are assumed to be exponentially distributed. If spots are unavailable when the customers arrive, they leave in order not to risk missing their flights.

The station manager is considering the option of hiring additional employees to deliver massages. The hourly wage of an employee is $50/hr. How many ADDITIONAL employees should the manager hire to maximize profits? [Profit = revenues from customers - labor cost] Suppose that there exists sufficient equipment to accommodate as many new employees as needed.

a. none

b. 1 additional employee

c. 2 additional employees

d. 3 additional employees

e.4 additional employees

f. There is not sufficient information to answer the question.