The justification for replacing a mechanic can be found when the Total Expected Cost
per piece formula shown as Equation (1) is applied. For this scenario the hourly rate for
the machine and its rate of production are fixed, having the hourly rate of the operator as
the only variable. The hourly rate of each available and feasible mechanic is entered into
Equation (1), with a replacement undertaken only when it yields a lower cost.
A reduction in total expected cost should not increase service time (i.e., increase the
unavailability of the machine). Thus the next part of this pre-emption strategy should
address: