Abby purchased $100$ shares of Mango Stock for a total of $$500$ three years ago. This year, Abby sells her $100$ shares of Mango for $$680.$ Which of the following concepts tells us that Abby needs to only include $$180$ from the sale of the stock in her gross? $$

personal and dependency exemption

like$-$kind exchange deferral

tax$-$free return of basis