Help Pls In isosceles triangle $ABC$ we have $AB=AC=4$. The altitude from $B$ meets $\overline{AC}$ at $H$. If $AH=3(HC)$ then determine $BC

In isosceles triangle $ABC$ we have $AB=AC=4$. The altitude from $B$ meets $\overline{AC}$ at $H$. If $AH=3(HC)$ then determine $BC$.