Your firm has purchased an injection molding machine at a cost of $100,000. The machine’s useful life is estimated at 8 years. Your accounting department has estimated the capital cost for this machine at about $25,455 per year. If your firm’s MARR is 20%, how much salvage value do you think the accounting department assumed at the end of 8 years?

A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. 
An 'information system' means a discrete set of information resources organized for the collection, processing, maintenance, use, sharing, dissemination, or disposition of information.

Engineering economics, previously known as engineering economy, is a subset of economics concerned with the use and "...application of economic principles" in the analysis of engineering decisions.