To find the unit rate, you need to divide the total miles traveled by the total hours taken.
Dr. Cranium traveled 2,800 miles in 5 hours, so the unit rate in miles per hour would be:
\[ \text{Unit Rate} = \frac{\text{Total Miles}}{\text{Total Hours}} = \frac{2800 \text{ miles}}{5 \text{ hours}} = 560 \text{ miles per hour} \]
So, the ratio of miles to hours (the unit rate) is 560 miles per hour.