A stone bridge has a parabolic arch where a river flows under it. At the water level the arch is 24 ft wide. The peak of the arch is 40 ft above the water.

A. Using the left end of the arch (where it meets the water) as the origin, find an equation for the arch. That is,find an equation that gives the height y (in feet) above the water of a point on the arch as a function the point's position x (in feet) in relation to the left endpoint.

B. A town along the river wants to place red warning lights on the arch at points 6 ft to the right of its left end and 6 ft to the left of its right end. At what height will the lights need to be placed?