3. Sketch a graph of a continuous function f(@) with the following properties: o f (a) is increasing on the interval (6, oo) o f (a) is decreasing on the intervals (-oo, 0) and (0, 6) . f (a) is concave downward on the interval (0, 4) o f () is concave upward on the intervals (-co, 0) and (4, co)