Optics: JEE Main 2026 Physics question

A prism of angle $75^\circ$ and refractive index $\sqrt3$ is coated with thin film of refractive index 1.5 only at the back exit surface. To have total internal reflection at the back exit surface the incident angle must be_______. ($\sin15^\circ=0.25$ and $\sin25^\circ=0.43$)