Use the given graph of the function f to answer the following questions. 18 1.8 1. Find the open interval(s) on which f is concave upward. Answer (in interval notation): 2. Find the open interval(s) on which f is concave downward. Answer (in interval notation): 3. Find the coordinates of the points of inflection. List your answers as points in the form (a, b). Answer (separate by commas)