If $f(x)=3 \sin x+4 \cos x$ what is $f(\large\frac{\pi}{4})$

Question

$\begin{array}{1 1} (a)\;\large\frac{1}{\sqrt 2} \\ (b)\;\large\frac{-1}{\sqrt 2} \\ (c)\;\large\frac{7}{\sqrt 2} \\ (d)\;\large\frac{-7}{\sqrt 2} \end{array}$