The Saint Louis Gateway Arch has shape of inverted catenary, the curve which is roughly shape of the parabola. Form ground level to vertex, Gateway Arch is 630 feet tall. At ground level legs are 630 feet apart. Legs extend 60 feet below ground level to anchor into bedrock. Given the information, find equation of the parabola which estimates shape of Gateway arch? Suppose that origin of coordinate system is at ground level midway between legs of arch. Write equation in standard form \(y=ax^2+bx+c\).