A key concept in the development of positive economic theories is the notion of "refutability"-a "theory" is not a "theory" unless there is some evidence that, if true, could prove it wrong. Use this notion to discuss whether one can conceive of evidence with which the following theories might be refuted:
a) Friedman's claim that pool players play as if they were using the rules of physics
b) The theory that firms operate so as to maximize profits
c) The theory that demand curves slope downward
d) The theory that adoption of capitalism makes people who are poor more miserable?