Let a function \( f : \mathbb{R} \to \mathbb{R} \) be defined as:Where \( b \in \mathbb{R} \). If \( f \) is continuous at \( x = 4 \), then which of the following statements is NOT true?
\( f \) is not differentiable at \( x = 4 \)
\( f'(3) + f'(5) = \dfrac{35}{4} \)
\( f \) is increasing in \( \left(-\infty, \dfrac{1}{8}\right) \cup (8, \infty) \)
\( f \) has a local minima at \( x = \dfrac{1}{8} \)
