A mountain climber stands at the top of a 52.8m cliff hanging over a calm pool of wat. The climber throws two stones vertically 1.9 s apart and observes that they cause a single splash when they hit the water. The first stone has an initial velocity of +1.9m/s. Find the velocity of the first stone at the instant both stones hit the water. The acceleration of gravity is 9.81m/s2. Answer in units of m/s.