Solve each part of given question:
Question: A galaxy known to be traveling away from the Earth at 0.840 percent of the speed of light is observed on Earth to have a strong peak in its spectrum at 656.1 nm. However, one small portion of the galaxy (a "dwarf") has a similar observed peak with a wavelength that is 4.08 nm shorter. (This situation is not as strange as it may sound. Several galaxies can be observed to be in the process of collision or merger, such as the Whirlpool Galaxy. Several others, particularly radio galaxies, often exhibit high-speed jets or lobes.)
Part I: Calculate the wavelength of the light emitted by the bulk of the galaxy.
Part II: What is the speed of the dwarf, relative to its "parent" galaxy? (Enter your answer as negative if the dwarf is moving toward Earth relative to the rest of the galaxy.)
Please provide any help is greatly appreciated!