Why are the majority of the world's economies mixed? what may happen to the "pure" types of economies (traditional, socialist/command, market capitalist) when they incorporate elements from other economic models?

Which of these best describes the function of a "super pac"? a)create bi-partisan legislation that can become law b)organization meant to reign-in spending of political candidates during election cycles c)promote the interests of supreme court justices without breaking specific tampering laws d)raise funds through donations from corporations or individuals to support or oppose specific political candidates