Determine the optimum preventive maintenance frequency for each of the equipment below if
breakdown times are Normally distributed:
Average Time (days) Standard
Equipment between Breakdowns Deviation (days)
A201 20 2
B400 30 3
C850 40 4
Preventive Breakdown
Equipment Maintenance Cost Cost
A201 $300 $2,300
B400 $200 $3,500
C850 $530 $4,800