听力原文： A friend of mine told me that when he was a young man, be went to work as a teacher in one of the states of India. One day, he received an invitation to dinner at the ruler's palace. Very pleased, he went to tell his colleagues. They laughed and told him the meaning of the invitation. They had all been invited and each person who was invited had to bring with him a certain number of silver and gold coins. The number of coins varied according to the person's position in the service of the government. My friend's income was not high, so he did not have much to pay. Each person bowed before the ruler. His gold went onto one heap his silver went onto another heap. And in this way he paid his income tax for the year. This was the simple way of collecting income tax. The tax on property was also collected simply. The ruler gave a man the power to collect a tax from each owner of land or property in a certain area, if this man promised to pay the ruler a certain amount of money. Of course, the tax collector managed to collect more money than he paid to the ruler. The difference between the sum of money he collected and the sum of money he gave to the ruler was his profit. What do we know about the speaker's friend?