Q:  What is the average apparent magnitude in the V filter for
              RR Lyrae stars in the Draco dwarf galaxy?

            The average of the V-band apparent magnitudes is about

                   m(V)  =  20.20



  Q:  The absolute magnitude of RR Lyrae stars in the V filter is approximately
              M(V) = +0.77

              What is the distance to the Draco dwarf galaxy?


           First, we compute the difference between apparent and absolute
           magnitudes, which is called the "distance modulus"

                   m(V) - M(V)  =  20.20 - (+0.77)  = 19.43  mag


           Next, we use the distance modulus formula to calculate the
           distance to the cluster:

                   (m - M)  =  19.43  =  5*log(d) - 5

                    5*log(d)  =  24.43

                      log(d)  =   4.89 

                       d      =   10^(4.89)  =  77,000 pc  =  77 kpc