Answer
${\bf 0.17 }\;\rm A$
Work Step by Step
The peak current is given by
$$I=\dfrac{\varepsilon_0}{Z}$$
where $Z=\sqrt{(X_L-X_C)^2+R^2}$,
$$I=\dfrac{\varepsilon_0}{\sqrt{(X_L-X_C)^2+R^2}}\tag 1$$
We are given that $\phi=+30^\circ$ which is given by
$$\tan\phi=\dfrac{X_L-X_C}{R}$$
Hence,
$$X_L-X_C=R\tan\phi$$
Plug into (1),
$$I=\dfrac{\varepsilon_0}{\sqrt{(R\tan\phi)^2+R^2}} $$
$$I=\dfrac{\varepsilon_0}{R\sqrt{(\tan\phi)^2+1}} $$
Plug the known;
$$I=\dfrac{(10)}{(50)\sqrt{(\tan30^\circ)^2+1}} $$
$$I=\color{red}{\bf 0.173}\;\rm A$$
