4A. What's the precise meaning of the statement that a certain function u is an ordinal utility function for the preference relation > of a certain consumer? 4B. Which one(s) of the following functions v(x, y) = 2x3y3 - 100, w(x, y) = 3(x + y) + 120, t(x, y) = 2xy -150 is an ordinal utility function for a preference relation which admits u(x, y) = 3x1/2y1/2 + 120 as an utility function? (a) w only (b) v and w (c) v and t (d) v, w and t (e) none of the previous four statements is correct