The supporting detail that would fit with the subtopic "purchase of camels" is "33 camels bought for $250 each"
Explanation:
This information refers to the article "The Desert Camel Experiment - Camels in America's Southwest " by Joe Zentner and how camels came to American territory from Egypt, in the subtopic of "purchase of camels" they mention that there was an exhaustive research to make the best investment as so it was when they paid $250 for each one of them, even when one died, but two colts were born in the way.
