please solve using excel and show all steps/equations

pe: 819 12. A milling department has 10 machines. Each operates an average of eight hours before requiring adjustment, which takes an average of two hours. While running, each machine can produce 40 pieces an hour. a. With one adjuster, what is the net average hourly output per machine? b. If machine downtime cost is $80 per hour and adjuster cost is $30 per hour, how many adjusters would be optimal