Driving along a highway, Megan noticed that her odometer showed 15951 (miles). This number is a palindrome - it reads the same forward and backward. Then 2 hours later, the odometer displayed the next higher palindrome. What was her average speed, in miles per hour, during this 2-hour period?
Answer Choices
A. 50
B. 55
C. 60
D. 65
E. 70