An arch for a bridge ovre ahighway is in the form of half of an ellipse .the top ofthe arch is 6m abve the ground level(the major axis).the high way has four label eahc 3.6 m wide center a center safety strip 2.4m wide ,and two sides strip2.4m wide and two sieds strip each 1.2m wide .what should the span of a bridge be .(the length of its major axis) if the height 8.4m from the center is tobe 3.9m
