y= f(x) Suppose that f is the differentiable function shown in the graph on the right and that the position at time t (sec) of a particle moving along a coordinate axis is s = f(x) dx meters. Use the 12 (9.9) (6,6) (15,6) graph to answer parts (a) through (9). 3- (3:3) -3 3 6 9 12 15 18 21 24 27 a. What is the particle's velocity at time t = 18? The velocity is because v(t) =