Economic systems differ according to which two main characteristics?

c, theres a double tax on the business earnings

answer; /// i believe the correct answer is (all of the above);

answer; (a) calling people who have not shown interest in the product and asking them to buy it;

answer; ///(d); determining who competes most closely   with whom evaluating whether industry driving forces and competitive pressure favor some strategic groups and hurt others, and ascertaining whether the profit potential of different strategic groups varies due to the strengths and weaknesses in each groups respective market positions;