please provide all values the question is asking for

thank You

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 Equipment A201 B400 C850 Average Time (days) between Breakdowns 17 33 34 Standard Deviation 2 4 4 Equipment A201 B400 C850 Preventive Maintenance Cost $220 $120 $ 470 Breakdown Cost $2,120 $3,420 $4,550 Click here for the Excel Data File Equipment Probability Ratio Z Interval (days) A201 B400 C850