Answer:
- 4.2 degrees
Explanation:
If the drop was from temp 0 at 8 pm to temp -16.8 at midnight (4 hours later)
then,the drop is given by the rate: -16.8/4 = - 4.2 degrees per hour
Therefore, at 9 pm the temperature was:
0 degrees - 4.2 degrees = - 4.2 degrees