T = R + (T0 − R)e-kt
T = temperature of the object after t minutes
T0 = initial temperature
R = temperature of the surroundings
k = cooling rate (depends on the object and conditions)
Suppose the temperature in Denver, Colorado was 55°F when a 5°F arctic cold front moved over the state. Using k = 0.012, how long would it take a puddle of water to freeze? (Recall that water freezes at 32°F.)