Find the open intervals where the function f(x)=-3x3+18x +169x -2is concave upward or concave downward. Find any inflection points. The function has a point of inflection at .(Type an ordered pair. Use a comma to separate answers as needed. Use integers or fractions for any numbers in the expression. Type N if the function does not have an inflection point.) The function is concave upward on the interval(s).(Type your answer in interval notation. Use a comma to separate answers as needed. Type N if the function is never concave upward.) The function is concave downward on the interval(s).(Type your answer in interval notation. Use a comma to separate answers as needed. Type N if the function is never concave downward.)