Read the following text carefully and answer the questions that follow: The girder of a railway bridge is a parabola with its vertex at the highest point, 10 m above the ends. Its span is 100 m.
a. Find the coordinates of the focus of the parabola.
b. Find the equation of girder of bridge and find the length of latus rectum of girder of bridge.
c. Find the height of the bridge at 20 m from the mid-point.