maximum: the point on a curve where the tangent changes from positive on the left to negative on the right
gresham's law: (economics) the principle that when two kinds of money having the same denominational value are in circulation the intrinsically more valuable money will be hoarded and the money of lower intrinsic value will circulate more freely until the intrinsically more valuable money is driven out of circulation; bad money drives out good; credited to Sir Thomas Gresham