PLS HELP (ASAP) actually give me the answer

You find a ring with a mass of
13.5g. You fill a graduated
cylinder with 10 ml of water and
put the ring into the cylinder. The
water rises to 15 ml. What is the
substance?

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.)