If sales N(x) are expressed as a function of the amount x spent on advertising, then the dollar amount at which N' (x), the rate of change of sales, goes from increasing to decreasing is call the [Select] (d, N(d)) is [Select] [Select] a critical point an equilibrium point a break-even point an inflection point a partition point If d is that dollar amount, then of N(x). [Select] break-even point global maximum vertex local maximum equilibrium point point of diminishing returns