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)=2x+x18 Solect the correct choice below and, if necessary, fill in the answer box to complete your cholce. A. The critical number(s) is(are) (Type integers or simplified fractions. Use a comma to separate answers as needed.) B. The function has no crifical numbers. Select the correct choice below and, it necessary, fill in the answer box to complete your choice. A. The function is increasing on (Type your answer in interval notation: Type integers or simplified fractions. Use a comma to separate answers as needed.) B. The function is never increasing. Select the correct choice below and, if necessary, fill in the answer box to complefe your choice. A. The function is decreasing on (Type your answer in interval notation. THe integers or simplifed fractions, Use a comma to separate answers as needed.) B. The function is never decreasing Select the correct choice below and, If necessary, fill in the answor bowes to complete your choice. (Type integers or simplified fractions.) A. The function has a local minimum f = and no local maximum. B. The function has a local maximum f= and a local minimum f= c. The function has a lecal maximum f = and no local minimum. D. The function has no local extrema