A famous math professor is found dead by his butler in his 50-room mansion. A student arrives on the scene at noon (12 P. M.) and immediately measures the temperature of the body to be 80 deg F. After 1 hour the student measures the temperature of the body again and finds it has fallen to 75 deg F. Assuming the professor’s original temperature was 98.6 deg F, and room temperature is a constant 70 deg F, how long before the student arrived on the scene did the professor die?