Astronomical observations of our Milky Way galaxy indicate that it has a mass of about 8.0 x10^11 solar masses. A star o

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Astronomical observations of our Milky Way galaxy indicate that it has a mass of about 8.0 x10^11 solar masses. A star orbiting near the galaxy's periphery is 5.9 × 10^4 light-years from its center.
A.) What should the orbital period ( in y) of that star be?
B.) If its period is 5.9 × 10^7 years instead, what is the mass (in solar masses) of the galaxy? Such
calculations are used to imply the existence of other matter, such as a very massive black hole at the center of the Milky Way.