A Bridge Support Arch Has the Equation $y=-\frac{1}{20}(x-30)^{2}+45$ Find the Length of the Arch If the Archis

A bridge support arch has the equation $y=-\frac{1}{20}(x-30)^{2}+45$ . Find the length of the arch if the archis $60.0 \mathrm{~m}$ wide at the base.