Two particles with masses m and 3m are moving toward each other along the x axis with the same initial speeds vi. particle m is traveling to the left, and the particle 3m is traveling to the right. they undergo an elastic glancing collision such that particles m is moving in the negative y direction after the collision at a right angle from its initial direction.

(a) find the final speeds of the two particles in terms of vi.

(b) what is the angle theta at which the particle 3m is scattered?