Determine the optimum preventive maintenance frequency for each of the pieces of equipment if breakdown time is normally distributed: (Round "Probability Ratio" to 4 decimal places, and all other answers to 2 decimal places. Negative values should be indicated by a minus sign.) Use Table Average Time (daya) Standard Equipment between Breakdowns Deviation 19 31 36 A201 B400 C850 Equipment A201 3400 C850 Preventive Maintenance cost 5240 $140 $490 Breakdown Cout $2,140 $3,440 $4,600 Click here for the Excel Data Eile Equipment Probability Ratio Interval (days) Equipment A201 B400 C850 Average Time (days) between Breakdowns 19 31 36 Standard Deviation 2 3 6 Equipment A201 B400 C850 Preventive Maintenance Cost $240 $140 $490 Breakdown Cost $2,140 $3,440 $4,600 Click here for the Excel Data File Equipment Probability Ratio z Interval (days) A201 0.1121 0.0407 0.1065 -1.23 -1.74 16.55 25.78 B400 C850 -1.25