Describe the optimum preventive maintenance frequency for each of the pieces of equipment if breakdown time is normally distributed:
Equipment Average Time (days) Standard
Between Breakdowns Deviation
A201 20 2
B400 30 3
C850 40 4
Equipment Preventive
Maintenance Cost Breakdown cost
A201 $300 $2,300
B400 $200 $3,500
C850 $530 $4800