[解析]
Dear Jim,
I am writing with good news.A video contest is going to be organized in our school soon,and knowing that you are such an expert in filming videos,I am wondering whether you would like to participate.(邀请他参加小视频大赛)
Topics like campus life,family life or the great changes that have taken place in your hometown ought to be covered in the video,which should not be longer than 8 minutes.【高分句型一】The deadline is December 10th,2017,and once you have created your video,you can just upload it to the school website.(作品的要求;参赛方式和截止时间)
It is a good chance to prove your talent in filming as well as an opportunity to share your works with more people.【高分句型二】I believe you won't regret doing it.Wish you good luck!(再次鼓励他参加)
Yours,
Li Hua