1. At minute 18 A catches up to B and begins to pass B. At minute 23 A catches up to B again. Explanation: A runs 400 meters more than B in 5 minutes. So the difference in speed between A and B is 400 ÷ 5 = 80 meters.

2. In the 15th minute A speed up, in the 18th minute A caught up with B and began to exceed B, that: A 3 minutes to catch up with B, the original difference between the two people: 80 × 3 = 240 (meters) This is the original B faster than the speed of the A speed caused by the beginning of the 15 minutes caused. So the original B speed faster than the speed of A: 240 ÷ 15 = 16 meters, now A speed faster than the speed of B 80 meters, indicating that the speed of A: 16 + 80 = 96 meters

3. Set the original speed of A x meters per minute, now the speed of A x + 96 meters per minute

15x + (x + 96) × (23 and 5/6-15) = 10,000

x=384

So it turns out that B's speed:384+16=400 meters

The time taken by B to run the whole course is:10000÷400=25 minutes

During the whole course, B is moving at a constant speed; in the first 15 minutes A is slow, and in the fifteenth minute A accelerates to the finish line

At the eighteenth minute A catches up with and begins to overtake B. At the twenty-third minute A again catches up with B and begins to overtake him. In the 23rd minute, A catches up with B again

It can be seen that after A speeds up, in 23-18=5 minutes, it is one lap more than B, i.e., 400 meters, so A travels 400÷5=80 meters per minute more than B

At the 23rd minute and 50 seconds, A arrives at the finish line, and at this moment, B should still be 80 meters/minute × (23 minutes and 50 seconds - 18 minutes) 1400/3 meters from the finish line

So B's speed is (10,000-1400/3) meters/(23 minutes 50 seconds)=400 meters/minute

So the time taken by B to run the whole course is 10,000/400=25 minutes