An alpha particle collides with an oxygen nucleus, initially at rest. The alpha particle is scattered at an angle of 25.0° above
its initial direction of motion, and the oxygen nucleus recoils at an angle of 50.0° below this initial direction. The final speed of the oxygen nucleus is 2.08×105 m/s. (The mass of an alpha particle is 4.0 u, and the mass of an oxygen nucleus is 16 u.) What is the final speed of the alpha particle?