AMC 10 2020b Problem 6

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? $\textbf{(A)}\ 50 \textbf{(B)}\ 55 \textbf{(C)}\ 60 \textbf{(D)}\ 65 \textbf{(E)}\ 70$