Setting boundaries for how many hours to work when Salary?

I interviewed for a salary position last week, and have a second interview with the person I'd be working directly for next week. I've always been an hourly employee so I'm not sure how the hours work with salary. How do you make sure you won't be taken advantage of and worked 50+ hours every week? How do you ask about that without sounding resistant/lazy? I'm okay with some extra hours through busy times but I'd hate to consistently work over 45 hours each week.

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