To find the unit rate in miles per hour, you divide the total distance traveled by the total time taken.
Given:
- Distance = 22,500 miles
- Time = 5 hours
Now, calculating the unit rate:
\[ \text{Unit Rate} = \frac{\text{Distance}}{\text{Time}} = \frac{22,500 \text{ miles}}{5 \text{ hours}} = 4,500 \text{ miles per hour} \]
Therefore, the correct answer is 4,500 miles per hour.