The speed of all light waves is 3.0 x 108 m/s (300,000,000 m/s). The green color shown corresponds to light with a wavelength of 5.4 x 10-7 m. What is the frequency of this color of light?

According to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does maria's voyage take according to samir?