If you know two locations that the kingpin in question frequents regularly (for most of us that is home & work), you can easily narrow down your haystack down t

If you know two locations that the kingpin in question frequents regularly (for most of us that is home & work), you can easily narrow down your haystack down to very few needles real fast. How many people live within 50m of your home and work within 50m of your office?