A woman dies in her air conditioned home. The ambient temperature is 74.6 F. You take her body temperatures: Skin: 70.6 F; Liver: 74.6 F; Scalp: 68.6 F; Underarm: 71.6 F; Mouth under tongue: 71.6 F. Her normal body temperature was 98.6 and she was not running a fever at death. Approximately how long has she been dead?