4. A spaceship descends towards earth. Before the spaceship reaches earth, its height :9 above the ground is given by y = at2 + [it + \"y where a, ,8, and 'y are arbitrary constants. a) What units must the constants a, ,8, and 7 have? b) Find the velocity and acceleration of the spaceship as a function of time. c) Initially at t 2 0 the position, velocity, and acceleration of the spaceship are y : IUOOm, 12y : 80m/s, and my : 3771/82. Find the appropriate values of the constants a, ,8, and "y. d) How long will it take for the spaceship to reach the ground and what is the velocity and acceleration when it does reach the ground