The local cable TV provider charges $89.00 per month for basic service, and has a $45.00 one-time "Activation Fee" for new accounts. Write (choose) the model for the Total Cost (C) of having cable TV as a function of the number of months (m) that you have service.

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?