This method is confusing. Any predicated method (a method ending in a question mark) is expected to return `true` or `false`. Also I don't think you want to use `inject` here - `inject` is used when summing a series of numbers, see http://blog.jayfields.com/2008/03/ruby-inject.html for more information.

I'm guessing what you want from this method is to ask which user is wearing the yellow jersey?

``` ruby
class Challenge < AR::Base
  def user_with_yellow_jersey
    users.order('activity_total desc').first
  end
end
```