please help answer this question

Trucks arrive at the loading dock of a wholesale grocer at the rate of 1 per hour. A single crew consisting of two workers can load a truck in about 40 minutes. Crew members receive $15 per hour in wages and fringe benefits, and trucks and drivers reflect an hourly cost of $80. The manager is thinking of adding another member to the crew. The service rate would then be 2 trucks per hour. Assume rates are Poisson The manager want to answer the question, "Would the third crew member be economical?" What would be the difference of average total costs (Truck drivers' wage during waiting + Crew members wage) per hour between two-member crew and three- member crew? And the answer for the question is Yes or No