A highly skilled surgeon claimed that he could replace a patient's brain with the brain of anyone possessing a professional expertise. Of course, the surgical fee depended on the type of professional brain being transplanted.

One day, a patient requested the doctor to replace his brain.

The doctor asked, "What kind of brain would you like to have?"

The patient shook his head and said, "I want the brain of a university professor. How much will that cost?"

The doctor replied, "The brain of an English professor costs 100,000 yuan per gram, while the brain of a history professor costs 200,000 yuan per gram."

Curiously, the patient asked, "What about a mathematics professor's brain?"

The doctor sighed and said, "Do you want the most expensive brain? The brain of a mathematics professor costs 1 million yuan per gram!"

The patient complained, "Why is the brain of a mathematics professor so expensive?"

With a smirk on his face, the doctor responded, "Do you have any idea how many mathematics professors it takes to collect one gram of brain?"