AHSME 1999 Problem 9

Before Ashley started a three-hour drive, her car's odometer reading was 29792, a palindrome. (A palindrome is a number that reads the same way from left to right as it does from right to left). At her destination, the odometer reading was another palindrome. If Ashley never exceeded the speed limit of 75 miles per hour, which of the following was her greatest possible average speed? $\mathrm{(A) \ } 33\frac 13 \mathrm{(B) \ }53\frac 13 \mathrm{(C) \ }66\frac 23 \mathrm{(D) \ }70\frac 13 \mathrm{(E) \ } 74\frac 13$