Iver audio is an all-in-one music management tool that was first marketed in 1999. most users can use the basic version that is free, but a $19.99 upgrade provides extra features such as supertagging, faster ripping and burning. which of the following explains this approach for applying freeconomics? a. gift economy approachb. cross subsidies approachc. zero marginal cost approachd. labor exchange approache. freemium approach