This is on the application of Differential Equations (Variable Separable Applications).

Ran Mori, who is a daughter of a famous detective, was preparing for a date with Conan Edogawa on a Sunday night. She went to her friend's room to borrow her hair curler, but she discovered Serena's dead body instead.

Although shocked to see her friend lying on the floor, she immediately took the temperature of the body at 10:00 pm which was 95.9F. She contacted everyone she can, and Conan was the first to come after two hours.

Conan took the temperature upon his arrival which is found to be 93.7F. He also noted the room temperature was constant at 68F. Ran was so curious to determine Serena's time of death. Help her know the time that her friend died assuming the victim's normal body temperature was 98.6F.