Question about raising

[nassaubayman]

Here's a scenario I see occasionally, but I rarely see the official answer addressed within anyone's official rules:

No Limit Tournament.

Blinds are 1 and 2.

Someone raises to 5 (BB of 2 + a raise of 3).

What is the minimum someone can re-raise?

I've seen two answers:
1. You must double the last person's bet from 5 to 10.

2. You must raise by at least the amount of the last action (which was a raise of 3). Therefore, the minimum raise must be 5 + 3 = 8.

[Ensano]

the answer is 2... by the amount of the last action..

[supafrey]

It's 8