A roller coaster is going along a path. Wheeee! At a certain time to sec, the roller coaster has position (in m) r(t0) = (5, 2, 13), velocity (in m/s) v(t0) = (-2, 3, 2) and acceleration (in m/s2) a(t0) = (7, -3,5). (a) What was the speed of the roller coaster at this time? (b) Was the roller coaster speeding up or slowing down? (c) Approximate the position of the roller coaster a quarter of a second later.