Identical 50uC charges are fixed on an x-axis at x= +/-3.0 m. A particle of charge q=-15uC is then released from rest at a point on the positive part of the y-axis. Due to the symmetry of the situation, the particle moves only along the y-axis and has kinetic energy 1.2 J as it passes the point (0, 4.0m). (a) What is the kinetic energy of the particle as it passes through the origin (0, 0)? (b) At what negative value of y will the particle momentarily stop?