(a) A life-size inflatable dummy, with a mass 20 kg,
falls from a distance of 1 parsec down to the surface of a main sequence
star 50 times the mass of the Sun.  Remember that the Sun has a mass
of 2.0 * 10^30 kg.  How much potential energy is released?  Remember
to use the mass-radius relation for main sequence stars to deduce the
diameter of this large star.  Remember also that 1 parsec = 3.1 * 10^16 m.

(b) If this main sequence star collapses into a black hole, and the
dummy falls from a starting distance of 1 pc all the way down to the event
horizon, how many times more or less potential energy is released than 
In Part (a) above?  Remember that the radius of a 
black hole event horizon is given by r = GM/c^2.

(c) About how much of the rest mass energy (E=mc^2) of the dummy is released
in its fall from 1 parsec down to the event horizon?