Let your interviewer know how you feel about the hours required for the position you're interviewing for. If this is the first time you have been presented with working hours information for the role, take a moment and respond genuinely.
Keep in mind that candidates willing to comply with the hours requirements are more likely to receive an offer. Also, it is acceptable to ask how often you will be expected to work beyond 40 hours if it is unclear when the question is asked. Finally, let your interviewer know if you already work beyond 40 hours and are comfortable with that style of working schedule.