Percent Error - Definition & Examples

Chris, Brandon and Libby are watching award-winning cows in a pasture. They all bet each other $10$ dollars that they can guess the correct number of cows in the pasture. Chris guessed $78$, Brandon guessed $64$, and Libby guessed $72$. After asking the farmer walking by, "How many cows are in your pasture?", the farmer said there were $74$. Calculate the percent error of each person. Who receives the money if the lowest percent error wins?