4. For this problem, recall that you are not allowed the use of a graphing calculator. If you use analytical methods to graph this function that's fine, but it must be completely clear how you produced the graph without using a graphing calculator. If you state the answers without any work I will assume you used a graph generated d I will give you a zero on this Let f(x) = 215 + 5x2. (a) Find the critical points of f. (b Find the intervals where the function is increasing/ decreasing. Reasoning must be shown. (c) shown. Find the intervals where the function is concave up/ concave down. Reasoning must be Find any local maxima/ minima of the function. Explain how you know which is which