1100- 1000- 900- O 800- The graph of a company's profit P(t) in dollars, 700- at month t is shown. 600- 500- Complete parts a and b below 400- 300- 200- 100- 0- 0 3 6 9 12 15 18 21 24 27 a. Estimate, to the nearest whole numbers labeled on the horizontal axis, any values of t where the second derivative is zero t=(Type a whole number. Use a comma to separate answers as needed.) b. List any values of t where the second derivative is the same as the first derivative. t=(Type a whole number. Use a comma to separate answers as needed )