The correct answer should be San Francisco is one-eighth as populous as New York; there are 60 deaths a week in the former and 500 a week in the latter—if they have luck.
The part if they have luck is the part that's verbal irony because there's nothing to be lucky about when people are dying. However, the usage is understood as figurative speech because they are lucky that no more people than that die.
GOOD LUCK AND HOPE IT HELPS U