Whenever I read articles like this, a couple of questions come to mind. Cumulative probability of being struck by one of these things within next 10, 20, etc. y

Whenever I read articles like this, a couple of questions come to mind. Cumulative probability of being struck by one of these things within next 10, 20, etc. years? What would we do if we did see one coming that was going to strike earth given 1 day, 1 week, 1 month, etc. lead time?