Practice 1　 Suppose your friend David Johnson in Washington has just got a Ph.D. in law. Write a letter of congratulation to him. Also tell him you will attend a meeting in Washington next month. Ask him whether he has any time to show you around the city.　 You should write approximately 100 words. Do not sign your own name at the end of the letter...Use “Wang Lin” instead. You don’t need to write the address.