Finding the area of a triangle if the distances from the centroid to the vertices are $3$, $4$, $5$

Question

Let $G$ be the centroid of $\triangle ABC$, and let $AG=3$, $BG=4$, $CG=5$. Find the area of $\triangle ABC$.

So I calculated the lengths of the diagonals which is $9$, $12$, $15$, but now I don't know what to do next.