What does this Rust snippet output?

1fn main() {
2    let pair = (Some(5), None::<i32>);
3    let s = match pair {
4        (Some(a), Some(b)) => a + b,
5        (Some(a), None) => a,
6        (None, Some(b)) => b,
7        (None, None) => 0,
8    };
9    println!("{}", s);
10}