A worker is currently responsible for tending two machines in a machine cluster. The service time per machine is 0.35 min and the time to walk between machines is 0.15 min. The machine automatic cycle time is 1.90 min. If the worker's hourly rate = $12/hr and the hourly rate for each machine = $18/hr, determine
(a) The current hourly rate for the cluster, and
(b) The current cost per unit of product, given that two units are produced by each machine during each machine cycle.
(c) What is the % idle time of the worker?
(d) What is the optimum number of machines that should be used in the machine cluster, if minimum cost per unit of product is the decision criterion?