How do you stop Erling Haaland? And if you successfully do that (West Ham didn't), how do you stop Rayan Cherki? Miraculously pass steps one and two and it's just the small matter of Phil Foden, Tijjani Reijnders and Bernardo Silva in your way.
West Ham failed every question in what is one of the toughest exams any side in the Premier League will face all season long: a title-contending City, at home, when they have wind in their sails.
Haaland's brace, both fortuitous in one aspect but ruthless finishes from the world's best finisher in the other, either side of half-time drew a robot celebration for the first and a smile-shrug of the shoulders combination for the second.