The time ratio between Party A and Party B is 8 to 6, which is 4 to 3, so the speed ratio between Party A and Party B is 3 to 4. When they meet, the driving time is the same. If the speed ratio is 3 to 4, the distance ratio is 3 to 4. A walked 3/7, B walked 4/7, and the distance from the midpoint is 0.5/7, which is equivalent to 25km, so the distance between A and B =25/(0.5/7)=350km.