To celebrate the launch of the 2021 Inc. 5000 list of America’s fastest growing private companies, Christine Lagorio-Chafkin interviews the co-founder and chief executive of Carbon Health, the startup aiming to make health-care more accessible and affordable--and which earned the No. 2 spot on the Inc. 5000 list with $45 million in 2020 revenue and an astounding 39,734 percent three-year growth rate.