Which One Is Better or Correct?

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Jun 01st 2012 14:14
I slept for only 8 hours in the last 40 hours.
I slept for only 8 hours in the past 40 hours.
I slept for only 8 hours durig the past 40 hours.
I slept for only 8 hours during the last 40 hours.

Could you tell me which one is correct or better?

Thank you!:D