Answer:
Rational is based on the logical preference. Being irrational does not means that the choice is made based on monetary preference. It is more logical than monetary.
Explanation:
The two friends took same courses in college but after the completion of college degree one decides to go for MBA and other pursues PhD in English. The expected earnings of MBA are higher than PhD but one of friend who chooses the PhD has not considered the logical decision making based on money. He might have chose the PhD because he is more interested in becoming a professor rather than a business professional.