An expensive piece of equipment is used in the masking operation for semiconductor manufacture.A capacitor in the equipment fails randomly. The capacitor costs $7.50, but if it burns out while the machine is in use, the production process must be halted. Here the replacement cost is estimated to be $150. Based on past experience, the lifetime distribution of the capacitor is estimated to be Number of Months Probability of of Service Failure 1 .08 2 .12 3 .16 4 .26 5 .22 6 .16 How often should the capacitors be replaced in order to minimize the expected monthly cost of planned and unplanned replacement?