A sales response function relates the _______ , and the form of the function is usually _______ .
A. Increase in revenue to relative increases in costs; convex.
B. Expense of marketing effort to the primary competitor's spending; U-shaped.
C. Expense of marketing effort to the marketing results obtained; S-shaped.
D. Market share of the firm to market share of the primary or nearest competitor; linear. incremental costs to market share; concave.
