帮忙写一篇英语小作文吧、急情景：史密斯夫妇邀请你周六晚上参加他们家举行的晚宴、但是正巧那天晚上你要去机场接友、故不能赴约

Dear Mr and Mrs Smith,
Thank you very much for inviting me to the dinner this Saturday. But unfortunately to tell you that I will not be able to arrive then, as I have to go to the airport to pick one friend.
I am really appriciate that you invited me, wish you enjoy your dinner then.
Kind regards
Yours Joan

等等

The scene: Mr. and Mrs. Smith invite you on Saturday night to participate in a dinner hosted by their home, but it happened the night you go to the airport to pick the Friends, it can not keep the appointment. Tasks: (Joan) about a 50 word letter written in English, an explanation and thank you