A centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers ${140}^0\mathrm{F}.$ What is the temperature as registered by the centigrade thermometer?

• A

  ${30}^0\mathrm{C}$

• B

  ${40}^0\mathrm{C}$

• C

  ${60}^0\mathrm{C}$

• D

  ${80}^{\mathrm{o}}\mathrm{C}$