Question 3 (1 point) If f ( x) =x3 (x2 - 56), then fis increasing on which one of the following intervals ? O a) (-0o, - V8) U (18, 00) O b ) ( - 0o , 0) u ( 18, 00 ) O c) ( - V 8, 0 ) U (0, V8 ) O d) (-V8, 0) O e) (0, V8) Question 4 (1 point) Using the first derivative test f (x) = x3 (x2 - 42 ) has local minimum number(s) at O a ) V6 O b ) 0 , V6 O c) - V6 O d) to O e) None of the above