Application Of Derivatives

Let $f(x)$ be a differentiable function, $A(0, \alpha)$ and $B(8, \beta)$ be two points on the curve $y=f(x)$. Given $f(0)=2$ and $f^{\prime}(4)=\frac{-3}{4}$. If the chord $A B$ of the curve is parallel to the tangent drawn at the point $(4, f(4))$, then $\beta=$