What are the solutions to the nonlinear system of equations below? check all that apply

y= -5x
x^2+y^2=26

a.) (26, -5)
b.) (-1, -5)
c.) (1, 5)
d.) (-26, 5)
e.) (1, -5)
f.) (-1, 5)

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?