The cable of a uniformly loaded suspension bridge hangs in the form of a parabola The roadway which ......

The cable of a uniformly loaded suspension bridge hangs in the form of a parabola. The roadway which is horizontal and 100 m long is supported by vertical wires attached to the cable, the longest wire being 30 m and the shortest being 6 m.
Find the length of a supporting wire attached to the roadway 18 m from the middle.      (5 marks)

By: santosh