How Does Galaxy Rotation and Recession Affect Observed Light Frequencies?

[gamesandmore]

A distant galaxy is simultaneously rotating and receding from the earth. As the drawing shows, the galactic center is receding from the Earth at a relative speed of uG = 1.5e6 m/s. Relative to the center, the tangential speed is vT = 0.3e6 m/s for locations A and B, which are equidistant from the center. When the frequencies of the light coming from regions A and B are measured on earth, they are not the same and each is different than the emitted frequency of 6.400e14 Hz.

Vt = wr
fo = fs (1 +- vrel/c)

No idea where to start

 

[Kurdt]

I am assuming that you have to work out what the measured frequencies of A and B are given their emitted frequency? You have the equation for finding the observed frequency compared to the emitted frequency:

f_o=f_s \left(1+\frac{v}{c}\right)

What is the relative velocity of points A and B from the Earth?