A layer of liquid $B$ floats on liquid $A$. A ray of light begins in liquid $A$ and undergoes total internal reflection at the interface between the liquids when the angle of incidence exceeds $36.5^{\circ} .$ When liquid $B$ is replaced with liquid $C$, total internal reflection occurs for angles of incidence greater than $47.0^{\circ}$. Find the ratio $n_{B} / n_{C}$ of the refractive indices of liquids $B$ and $C$.