Can I get help on these physics questions

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.)

1which body contains the majority of the mass in the solar system earth jupiter the moon the sun 2 what keeps the objects in the solar system such as planets orbiting around the sun the force of gravity the galaxy exerts on all objects within it including the solar system the great distance between the sun and the planets the sun's nuclear fusion which acts on each object the gravitational force between the sun and each object in the solar system

A15,000 kg rocket traveling at +230 m/s turns on its engines. over a 6.0 s period it burns 1,000 kg of fuel. an observer on the ground measures the velocity of the expelled gases to be −1,200 m/s.