x +23x + 124 2x - 26 f(x) = f" ( x) = x +22x + 121 (x+11)" Determine the concavity of f. Select the correct choice below and, if necessary, fill in the answer boxes to complete your choice. A. The curve is concave down on ( - co,13) and concave up on (13,co) (Type your answers in interval notation.) O B. The curve is concave up for all real numbers. O C. The curve is concave down for all real numbers