How the fuck am I supposed to know what key it's in when the key signature isn't even a key that's related to the key in the title, and the final chord makes no sense with any of the keys in question, and I don't have any musical instruments so I can't just fucking play it and hear what it sounds and feels like, and I'm sorry but I was trained as an instrumentalist and can't sight sing????

Perhaps it's reasonable to assume that a theory student might have access to an instrument, but you can't bring instruments into the exams (or start singing in the middle of an exam) and this book does say it's for exam preparation, so they should provide us with the tools to work out the example without an instrument! GAH!