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Wherever the second derivative changes sign, the function has an inflection point. If the second derivative does not change sign, you do not have an inflection point. MULTIPLE CHOICE PROBLEMS: 21. The volume of a hot air balloon is given by V (t) = =(9 - 2t)3 ft3/ hr. Find the rate of change of the surface area of the balloon when t = 3 hours. A. -961t ft2 / hr B. -48nt ft2 / hr C. -361t ft2 / hr D. -24nt ft2 / hr 22. A point P(x, y) moves on the graph of y2 = 2x3 such that " = x. Find dx/dt at the point dt