If f x x 3x 28 x 4x 21 Select the correct answer below O f g x O f g x O f g x O f g x O f g x O f g x x 4 x 2 and g x 2 find f g x and any domain restrictions for f g x x 4 x 2 x 4 x 2 x 4 x 2 x where a 7 3 2 X where 7 3 2 4 2 where x 7 3 2 x 4 x 2 where x 7 3 2 where x 7 3 2 where x 7 3 2