I mark as brainliest

Can somebody me out with this question

The center of the circumscribed circle lies on line segment and the longest side of the triangle is equal to the of the circle.

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?