Explain whether the following is a valid argument 

(a) A firm is a monopoly in a market and argues that demand is very elastic and therefore the market is relatively efficient 

(b) A firm is a monopoly in a market and argues that due to decreasing returns to scale, a single firm has lower cost than multiple competing firms. 

(c) A firm says they have large markups and argue this could increase dynamic efficiency due to the incentive to innovate 

(d) A firm is a monopoly in a market and argues that this ensures that the firm maximizes productive efficiency