If the Wavelength of a Monochromatic Source Is 490 Nm

Multiple Choice

If the wavelength of a monochromatic source is 490 nm in vacuum,what is the wavelength from the same source when it passes through a liquid where the speed of light is 2.40 x 10⁸ m/s? (c = 3.00 x 10⁸ m/s)

A) 671 nm
B) 612.5 nm
C) 490 nm
D) 392 nm