Use the properties of the globular clusters below to estimate
the mass interior to their radial position.

   We assume circular orbits, so

                       v^2 * R
           M(int)  =  -----------
                          G


    Cluster         R (kpc)     velocity (km/s)    Mass (solar)
---------------------------------------------------------------------

    47 Tuc           7.5           186               0.6   x 10^(11)

    Pal 1           17             211               1.8   x 10^(11)

    AM 4            25             238               3.3   x 10^(11)

    Pal 3           98             158               5.7   x 10^(11)

---------------------------------------------------------------------