Exact Equations & Substitutions · Easy problem

The equation $\left(2 x y\right)dx + \left(x^{2} + 3 y^{2}\right)dy = 0$ is exact. Its solution through the point $(1, 2)$ has the form $F(x, y) = C$ with $F = x^{2} y + y^{3}$. Find $C$.