Answer:

Step-by-step explanation:
As we know that bat emits the sound when it was at distance of 20.0 m from the wall
so the time taken by the sound to reach the wall is given as


Now in the same time distance moved by bat is


now distance between bat and the wall is given as

now since reflected sound and bat both moving towards each other so here time taken to reach the sound again on bat is given as



so total time taken is given as

