An injector machine goes down roughly 20% of the time (the injector gums up and needs to be cleaned, a quick process). One operator is assigned to service three identical such machines. Each machine can produce 100 parts/hr if running properly (i.e. not down). The operator is paid $10.00/hr and each machine costs $20.00/hr to operate. What is the unit cost for this operation? Is it worth hiring another operator at the same rate to assist the first operator, in case more than one machine goes down at the same time? What is the unit cost now?