Light travels through air at $3.0 \times 10^8\,\text{m s}^{-1}$. When a transparent plastic material is in air, the critical angle for light is $37^\circ$. Determine the speed of light in the plastic material.
- A$1.8 \times 10^8\,\text{m s}^{-1}$
- B$2.4 \times 10^8\,\text{m s}^{-1}$
- C$3.8 \times 10^8\,\text{m s}^{-1}$
- D$5.0 \times 10^8\,\text{m s}^{-1}$