NA 
A cup of boiling water ($212$\textsuperscript{◦}F) is placed to cool in a room whose temper- ature remains constant at $68$\textsuperscript{◦}F. Suppose the difference between the water temperature and the room temperature is halved every $5$ minutes. What is the water temperature, in degrees Fahrenheit, after $15$ minutes? 

  - $$77$$ 
  - $$86$$ 
  - $$92$$ 
  - $$98$$ 
  - $$104$$ 