The vector position of a particle varies in time according to the expression r = 3.40 1 - 5.20tz j where r is in meters and t is in seconds. (a) Find an expression for the velocity of the particle as a function of time. (Use any variable or symbol stated above as necessary.) 6.21 m/s X (b) Determine the acceleration of the particle as a function of time. (Use any variable or symbol stated above as necessary.) m/s2 (c) Calculate the particle's position and velocity at t = 4.00 s. m X m/s X