Gas prices are at the lowest level since 2021, according to AAA, as millions of Americans are traveling for the holidays. The average price of gas has been below $3 a gallon for most of the month. Plus, from "Marketplace Tech," ChatGPT has become the new WebMD. And from the Marketplace podcast "How We Survive," we learn what an invisible longitudinal line has to do with farmers, the economy, and the global food supply.