51. A nucleus, initially at rest. decays radioactively. In the process, il emils an electron horizontally to the east. with momentum 9.0 x 10 " kg m/s and a neutrino horizontally to the south, with momentum 4.8 x 10 " kg m/s. (a) In what direction does the residual nucleus move? [3] (b) What is the magnitude of its momentum? [3] (c) If the mass of the residual nucleus is 3.6 x 10"kg. what is its recoil velocity? [2]