A tool-crib with one attendant serves a group of 10 mechanics. Mechanics work for an exponentially distributed amount of time with mean 20 minutes, then go to the crib to request a special tool. Service times by the attendant are exponentially distributed, with mean 3 minutes. If the attendant is paid $6 per hour and the mechanic is paid $10 per hour, would it be advisable to have a second attendant?