The graph below is of f(x) for some function f(x) with domain (-,)(i.e., the graph of the derivative of f(x)).(a) What are the critical values of f(x)?(Enter your answers as a comma-separated list. If an answer does not exist, enter DNE.)(b) On what intervals is f increasing? (Enter your answer using interval notation.)(c) On what intervals is f decreasing? (Enter your answer using interval notation.)If f(x) has a domain of (-,4)(4,),f'(x)=x2-x-2(x-4)2, and f''(x)=8-7x(x-4)3, determine the following(a) The intervals on which f(x) is increasing/decreasing.(b) The location of all local extrema of f(x).