I need help asap can anyone help

Standard deviation of 19,29,21,22,23

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?

In which direction does the left side of the graph of this function point? a(x) = 3x - x2 + 4x - 2