Dear Lan,
 I am very happy to send you my birthday invitation.  This birthday will take place next Saturday night, March 17th, and everyone in our class will be present.  This will be a themed party, where people dress up as characters from fairy tales like princes and princesses, and I hope you find this idea interesting.  The party will start at 6pm, but I hope you can come a little early so we can help finish each other's outfits.
 Feel free to contact me if there is any change or inconvenience
 I look forward to hearing from you soon
 Sincerely
 Mai