Answer: Dr. Bostwick was able to provide medical services that did not satisfy his own wants, so he exchanged those services for money that he used to buy things that did. Professor Boudreaux had money but desperately wanted a pediatric gastroenterologist to treat his son.
Explanation:
Trade generates value by transferring goods or services from those who value them less to the people who need them more. The only way people can decide to specialize in the making of a single good or service is because they already know they can trade it for other goods they do need.
In the video 'How the Division of Knowledge Saved My Son's Life', Professor Boudreaux explains that it was thanks to Dr. Bostwick specialization on pediatric gastroenterology that his son´s life was saved.