On average, in men, 39 mL per kilogram of body weight is blood plasma. In women, 40 mL per kilogram of body weight is blood plasma. Rob weighs 80 kg, and Kristen weighs 60 kg. How many more milliliters of blood plasma does Rob have than Kristen?

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?