Coase (1937) addressed the question of why firms exist in a market economy. Which statements are consistent with his argument?

Coase (1937) addressed the question of why firms exist in a market economy. Which statements are consistent with his argument? 

a)There are costs to doing business by using the market.

b)In some cases firms can perform activities internally at lower costs than can be achieved through markets.

c)The source of this advantage is the firm’s ability to direct, through hierarchy and authority, resources more efficiently than could be performed through the market.

d)The ultimate size of firms is likely determined by the onset of diminishing returns to management.

e)All of the above.