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In this short story, two men -- one more by the book and the other less so -- are the crew on a cargo ship. An accident takes out their oxygen reserves, leaving only enough for one of them to make it back. One detail I can recall: the more easygoing one allows himself the occasional cigarette, infuriating his crewmate. Only the easygoing one survives, and it's one of those mystery reveal type stories where we find out the end of the story before we learn what happened. It possibly may be by Arthur C. Clarke, but just as possibly not. It's driving me nuts not being able to remember! Thank you in advance!