9 points. Let S(t) be the function which specifies the distance (in km) from a runner to the start line at time t (in hours) of a race. The graph of S(t) is given below: 4 y (km) 3 2 1 S(t) t (h) 3 Use the graph to give approximate answers to the following problems. (a) When was the runner running the fastest? (b) What happened between times 3 and 4? (c) What is the meaning of S-(1)?