A mechanical engineer is considering two types of pressure sensors for the low-pressure steam lines in several of the company plants. Piezoresistive sensors use the change in conductivity of semiconductors to measure the pressure. Fiber optic sensors use the properties of fiber optic interferometers to sense nanometer scale displacement of membranes. The costs for each system are shown below. Which should be selected based on a present worth comparison at an interest rate of 1% per month?

Piezoresistive Fiber Optic Purchase cost, $ 13,650 22,900 Maintenance cost, $/month 200 50 Salvage value, $ 0 2,000 Life, years 2 4