6 B (15 points) Consider two particles of mass m1 and in2 that are initially at rest at time t = D and separated by a distance r\". These particles gravitationally attract each other as the only force acting in the problem. For time t > I)1 the}r will move toward each other due to their gravitational attraction and eventually collide with one another. a) Derive an expression for the speed of each particle 'ulfr) and tug-(r) as a function of their separation distance 1* before they collide (Le. when I]