The position, y, of the midpoint of a guitar string can be modelled by the function y = 0.05 cos(880m/), where y is the distance, in centimetres, and / is the time, in seconds. Find the formulas for the velocity and acceleration of the string. (APP. 14)The half-life of a radioactive substance is 140 days. An initial sample is 300 mg. a) Find the mass, to the nearest milligram, that remains after 50 days. b) After how many days will the sample decay to 200 mg? c) At what rate, to the nearest tenth of a milligram per day, is the mass decaying after 50 days