A Consumer Maximizes Satisfaction at the Point Where His Valuation

Multiple Choice

A consumer maximizes satisfaction at the point where his valuation of good X, measured as the amount of good Y he would willingly give up to obtain an additional unit of X, equals:

A) the magnitude of the slope of the indifference curve through that point.
B) one over the magnitude of the slope of the indifference curve through that point.
C) P_X/P_Y
D) P_Y/P_X