For every pair of integers \(a\), \(b\), we define an operator \(a\otimes b\) with the following three properties.
1. \(a\otimes a=a+2\);
2. \(a\otimes b = b\otimes a\);
3. \(\frac{a\otimes(a+b)}{a\otimes b}=\frac{a+b}{b}.\)
Calculate \(8\otimes5\).