19)C14M.5 In a certain physics experiment, a helium atom traveling at a speed of 240 m/s hits an oxygen atom at rest. If the helium atom rebounds elastically from the oxygen atom at an angle of 90" with respect to its original direction of motion, what are the final velocities of both atoms (magnitude and direction)? (Hint: The mass of the oxygen atom = 4 times that of the helium atom.)