A Brillouin light scattering experiment was carried out in a 180-degree scattering geometry with a probe of 433 nm wavelength. The measured Brillouin frequency shift for an unknown material was found to be f = 0/27 = 18.4 GHz. In a separate measurement using an Abbe refractometer, the refractive index for the same material was measured to be n=1.44. Based on the parameters provided, find the material's speed of sound in m/s