please solve

5. (4p.) The position of a particle along the x axis depends on the time according to the equation x = At - Bt' where x is in meters and t is in seconds. (a) What SI units must A and B have? For the following, let their numerical values in SI units be 9.0 and 3.0, respectively. (b) At what time does the particle reach its maximum positive x position? (c) What total path-length does the particle cover in the first 2 seconds? (d) What is the average velocity and the average speed for the time interval 0 to 2 s