Find the critical numbers, the intervals on which f(x) is increasing, the intervals on which f(x) is decreasing, and the local extrema. Do not graph. f(x)=3x+ 147 X Select the correct choice below and, if necessary, fill in the answer box to complete your choice. A. The critical number(s) is (are) 7, -7. (Type integers or simplified fractions. Use a comma to separate answers as needed.) OB. The function has no critical numbers.. Select the correct choice below and, if necessary, fill in the answer box to complete your choice. A. The function is increasing on 7sx,xs-7 (Type your answer in interval notation. Type integers or simplified fractions. Use a comma to separate answers as needed.)