Dear Ms. Smith,

I'm Li Hua , the chair of the Students’ Union of Yucca Middle School , which is close to your university . I'm writing to invite you to be a judge at our English speech contest which will be held in our school on June 15 . It will start at 2：00 pm and last for about three hours . Ten students will deliver their speeches on the given topic "Man and Nature". We hope that you will accept our invitation if it is convenient for you . Please call me at 44876655 if you have any questions .

I am looking forward to your reply .

With best wishes,

Li Hua