What is the regression equation of a parabola with a maximum, if the vertex is x-5 y-10 and the points are x-2 y-8 x-9 y-7 x-10 y-5 x-11 y-1

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?