The Clever Engineer and the Persistent Doctor

Once upon a time, there was an architect who worked for a contracting company. But one unfortunate day, the company declared bankruptcy, leaving the architect suddenly unemployed. Despite searching high and low for a job that matched his expertise, he couldn't find a suitable position. Determined to make a living, he came up with a unique idea—he opened a medical clinic, counting on his wit and cleverness to succeed. To attract patients, he put a sign on the clinic door: "We will treat your illness for $200, and if you don't recover, we will pay you $400."
One day, a doctor from a neighboring clinic passed by and noticed the sign. Amused and intrigued, he saw an opportunity to exploit this “doctor” and earn an easy $400. He stepped into the clinic and greeted the architect, who was now playing the role of a doctor.
"Doctor, I've lost my sense of taste," the real doctor said with a sly smile. "Can you help me?"
The engineer-doctor replied, "Of course, don’t worry!" He turned to the nurse and asked her to bring "medicine number 6." As soon as the doctor took a sip, he spat it out, exclaiming, "This is gasoline! What are you giving me?"
The engineer grinned and replied, "Ah, you see? Your sense of taste has returned. That will be $200."
The doctor, frustrated and embarrassed, paid the $200 but resolved to get his revenge. Four days later, he returned to the clinic with a new plan. "Doctor, I seem to have lost my memory. Can you help me?"
The engineer remained unfazed. "Not a problem, sir. Just relax." He then instructed the nurse to bring him "medicine number 6" again. The doctor, remembering the taste of gasoline, protested, "Wait! That’s gasoline!"
The engineer smiled and replied, "See, your memory has returned! That will be $200."
Now angrier than ever, the doctor grudgingly handed over the fee, determined not to be outsmarted again. But his competitive spirit drove him to return one last time with a foolproof scheme.
A few days later, he returned to the clinic with another “ailment.” He told the engineer, "Doctor, I’ve lost my sight. I can’t see a thing. Can you help me?"
The engineer sighed and replied, "Unfortunately, sir, I can’t treat vision problems, so I’ll have to give you $400." The doctor grinned in satisfaction, feeling victorious as the engineer instructed the nurse to give him the payment.
But when the doctor looked down, he saw that he had received only $200. Outraged, he shouted, "This is only $200! You promised me $400!"
The engineer looked at him with a smirk and said, "Ah, so it seems your sight has returned after all. That will be $200, please."
Realizing he’d been bested yet again, the doctor admitted defeat. He paid the $200, accepted that he could never outwit the clever engineer, and walked away, never to return.