f(x)=x^(2)+cos(ax) a=6 Using the graph picture: Pick one reasonable value for a, but make it something larger than 2. a) Using calculus and the graph, find all critical values of f (x) on the given interval. b) Determine the interval(s) where the graph of f(x) is increasing and interval(s) where the graph of f(x) is decreasing. c) Find all inflection points of f(x). d) Using part c) determine the interval(s) where the graph of f(x) is concave up and the interval(s) where the graph of f(x) is concave down