VoiceSys,Inc

VoiceSys,Inc.produces voice mail switchboard systems used in large office buildings,hotels,and other facilities.VoiceSys's products are selling so well that the company has decided to buy new equipment that will increase its production capacity.This example best illustrates

A) why the demand for a particular seller's equipment is inelastic.
B) derived demand.
C) why the industry demand for this kind of equipment is quite elastic.
D) that the market for installations is a "boom or bust" business.
E) All these answers are correct.