On January 22 in 1943, the town of Spearfish, South Dakota, set the record for the world’s fastest temperature change.
At 7:30 a.m., the temperature was -4°F.
By 7:32 a.m., the temperature was 45°F.
By 9:00 a.m. the same day, the temperature was 54 °F.
By 9:27 a.m., the temperature was -4 °F.
How many degrees did the temperature change each minute from 9:00 to 9:27?