Passage Summary: A dairy farmer is making his cows more comfortable with mattresses, not just to be nice, but because comfortable cows produce more milk and make the farm more money.

Reasoning: Improving the comfort of cows (via mattresses) increases their blood flow, which in turn increases milk production and leads to higher profits for the farm.

Analysis: This stimulus describes a scenario where an action that benefits the welfare of others (the cows) is motivated by the self-interest of the actor (the farmer). It's a classic 'enlightened self-interest' model. When looking for the best-illustrated principle, seek a proposition that suggests improving the conditions or well-being of those one manages or employs can be an effective strategy for increasing one's own success or profit.