I need help with these questions.

The following graph shows the approximate value of the U.S. Consumer Price Index (CPI) from September 2004 through November 2005. CPI Sep 2004-Nov 2005 202A 200 198 196 194 192 190 188 0 2 4 6 8 10 12 14 Sep-04 Jan-05 Nov-05 The approximationg curve shown on the figure is given by I(t) = -0.005t3 + 0.12t2 - 0.01t + 190 (0 s t s 14), where t is time in months since the start of September 2004. (a) Use the model to estimate the monthly inflation rate in February 2005 (t = 5). [Recall that the inflation rate is I'(t)/I(t).] (Round your answer to three decimal places.) % (b) Was inflation slowing or speeding up in February 2005? slowing down speeding up (c) When was inflation speeding up? When was inflation slowing? HINT [See Example 3.] (Use the model to determine this.) Inflation was speeding up prior to ---Select--- 2005 and slowing after ---Select--- 2005.Find the t-coordinates of all critical points of the given function. Determine whether each critical point is a relative maximum, minimum, or neither by first applying the second derivative test, and, if the test fails, by some other method. f(t) = -5+ + 4t f has a relative maximum |% at the critical point t = 4 V 15 X . (smaller t-value) f has a relative minimum | % at the critical point t = 4 15 x . (larger t-value)Find the x-coordinates of all critical points of the given function. Determine whether each critical point is a relative maximum, minimum, or neither by first applying the second derivative test, and, if the test fails, by some other method. f(x) = 4x4 - 4x3 f has ---Select--- at the critical point x = (smaller x-value) f has ---Select--- at the critical point x = . (larger x-value)