A rock climber stands on top of a 53{\rm m} -high cliff overhanging a pool of water. He throws two stones vertically downward 1.0{\rm s} apart and observes that they cause a single splash. The initial speed of the first stone was 2.5{\rm m}/{\rm s} .How long after the release of the first stone does the second stone hit the water? What was the initial speed of the second stone? What is the speed of the first stone as it hits the water? (Please show your work!)