Using the data from Solved Problems 11.11, we can compare the costs for having one, two, or three librarians as follows: System k Labor Cost/min. Single server 1 $0.50(1) 5 $0.50 Two-server L Waiting Cost/min. $0.33(5) 5 $1.65 5 2 $0.0.50(2) 5 $1.00 1.008 $0.33(1.008) 5 $0.33 Three-server 3 $0.0.50(3) 5 $1.50 0.856 $0.33(0.856) 5 $0.28 Total Cost/min. $2.15 $1.33 $1.78 The system having the lowest cost is the two-server system; therefore, the best decision is to hire one additional librarian