Use short notes and illustrations to answer the following questions:

i) Distinguish between an indifference curve and an isoquant

ii) Distinguish between substitution and income effect of a price fall for a normal good.

iii) Distinguish between internal and external economies of scale

iv) What is the law of diminishing returns and state the conditions under which it is tenable

v) The profit-maximizing output for a firm is at the point where MR = MC, illustrate and comment for the case of a firm that faces a downward-sloping demand curve.