IT’S URGENT!! PLEASE HELP! Dan builds identical model cars and sells them online. He records the number of models he completes every couple of hours. The graph shows Dan’s data. Choose two pairs of points on the line and calculate the slopes between them. Is Dan’s productivity constant? Explain.

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?