The surplus is 1760/2=880.

B keep it at 1760-720= 1040.

When the speed ratio of Party A and Party B becomes 9: 1 1, let the speed of Party A be 9m/s and that of Party B be1/m/s,

Then: A left 880/9 = 97.78.

B walked the whole journey of1040/11= 94.5445.

The time unit difference is 97.77778-94.5454=-3.23233.

So b arrived first;

(Hope to adopt)