An electronic equipment contains 500 resistors. When any resistor fails, it is replaced. The cost of replacing a resistor individually is ! 20.00. If all the resistors are replaced at the same time, the cost per resistor is ! 5.00. The percent surviving, S(i) at the end of month i is given in the following table.

Per cent Survival Rate Month i 0 1 2 3 4 5 S(i) 100 90 75 55 30 0 What is the optimum replacement plan?

AppendixLO1