Hot tea is brought to a boil at 212°F and must be cooled to a temperature of 160°F. The room temperature is 68°F.

Newton's law of cooling can be used to find how long it takes a liquid to be cooled. The formula is:

\[ T = (T_0 - T_r)e^{-rt} + T_r \]

where:
- \( T_r \) is the air temperature,
- \( T_0 \) is the initial temperature,
- \( T \) is the expected temperature,
- \( r \) is the rate of cooling, and
- \( t \) is the time in minutes.

How long does it take for tea to cool if the rate of cooling is 0.05?

A. 3.9 minutes
B. 9.0 minutes
C. 12.9 minutes
D. 37.9 minutes