Given the following function, (a) find the vertex; (b) determine whether there is a maximum or a minimum value, and find the value; (c) find the range; and (d) find the intervals on which the function is increasing and the intervals on which the function is decreasing. f(x) =x2 + 8x47 (a) The vertex is (4,-9). (Type an ordered pair, using integers or fractions.) (b) Determine whether the parabola has a maximum value or a minimum value and find the value. Select the correct choice below and fill in the answer box within your choice. (Type an integer or a fraction.) A. The parabola opens downward and has a maximum value of B. The parabola opens upward and has a minimum value of