Question: 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
![898_failure.png](https://secure.tutorsglobe.com/CMSImages/898_failure.png)
How often should the capacitors be replaced in order to minimize the expected monthly cost of planned and unplanned replacement?