Consider a spiral galaxy that is a little bit bigger than the Milky Way, with a mass of luminous matter of 4 10^11 M. Suppose you measure the velocity of faint gas far from the edge of the luminous disk at a distance from the galaxy center of 65 kpc to be 300 km s^1. The mass enclosed inside the orbit of this gas is 1.36*10^12 M_sun. What is the amount of dark matter inside of 65 kpc (in units of M_sun)