A vehicle factory manufactures cars. The Unit Cost C (the cost in dollars to make each car) depends on the numbers of cars made. If x cars are made, then the unit cost is given by the function C(x) = 0.4x^2 - 96x +16541. What is the minimum unit cost?

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?