Please help If something is shot straight up in the air at a speed of 70 m/s, how much time before it will hit the ground? (when I calculated it I got 14 is it right?) My following question is if the object from number 2 is shot up (70m/s) in the air how high will it get?

When a vertical beam of light passes through a transparent medium, the rate at which its intensity i decreases is proportional to i(t), where t represents the thickness of the medium (in feet). in clear seawater, the intensity 3 feet below the surface is 25% of the initial intensity i0 of the incident beam. what is the intensity of the beam "10" feet below the surface? (give your answer in terms of i0. round any constants or coefficients to five decimal places.)