I need solve this question

Over a time interval of 2.01 years, the velocity of a planet orbiting a distant star reverses direction, changing from +21.3 km/s to -16.5 km/s. Find (a) the total change in the planet's velocity (in m/s) and (b) its average acceleration (in m/s2) during this interval. Include the correct algebraic sign with your answers to convey the directions of the velocity and the acceleration. (a) Number i Units C (b) Number i Units