Arunner is jogging in a straight line at a steady vr= 5 km/hr. when the runner is l= 7.5 km from the finish line, a bird begins flying straight from the runner to the finish line at vb= 20 km/hr (4 times as fast as the runner). when the bird reaches the finish line, it turns around and flies directly back to the runner. what cumulative distance does the bird travel? even though the bird is a dodo, assume that it occupies only one point in space (a "zero" length bird), travels in a straight line, and that it can turn without loss of speed. answer in units of km.