Read Sino-US Tax Treaty of 1984
1/ See article 17 and 18.
IRS website:
http://www.irs.gov/Businesses/International-Businesses/China---Tax-Treaty-Documents
Chinese-English text
http://blog.sina.com.cn/s/blog_4dae264e0100uhik.html
2/ Not sure what you mean by "到底是五萬還是一萬要報?"