Kao measured the temperature of a cup of hot chocolate placed in a room with a constant temperature of 70 degrees Fahrenheit (${}^{\circ}$F). The temperature of the hot chocolate was 185${}^{\circ}$F at 6:00 p.m. when it started cooling. The temperature of the hot chocolate was 156${}^{\circ}$F at 6:05 p.m. and 135${}^{\circ}$F at 6:10 p.m. The hot chocolate's temperature continued to decrease. Of the following functions, which best models the temperature $T(m)$, in degrees Fahrenheit, of Kao's hot chocolate $m$ minutes after it started cooling?