3. During a 15K race, runners A and B run with average speed of 5 m/s. for the first 5K of the race. During the last 10K of the race, runner A, runs with an average speed of 4.27 m/s while runner B runs with an average speed of 4.39 m/s. a) If they start at the same time, how far apart the runners are upon completion by the runner B? b) If the two runners' wish to finish at the same time, how much head start runner A should get?