The Draco galaxy is a dwarf galaxy within the Local Group. Its luminosity is L=(1.8±0.8)×105L⊙ and half its total luminosity is contained within a sphere of radius rh=120±12 pc. The red giant stars in the Draco galaxy are bright enough to have their line-of-sight velocities measured. The measured velocity dispersion of the red giant stars in the Draco galaxy is σr=10.5±2.2 km s−1. What is the mass of the Draco galaxy? What is its mass-to-light ratio? Describe the possible sources of error in your mass estimate of this galaxy.