As given by the question
There are given that the first bounce is 6.7.
Now,
81% of the first bounce is:

The,
The next bounce is the addition of 81% of the first bounce
So,

Now,
The third bounce is addition of 81% of the second bounce
So,

The third bounce is 9.4878 ft
Now,
For the fourth bounce

Now,
For the fifth bounce

Now,
For the sixth bounce:

So, the height of the sixth bounce is 2.546
Hence, the correct option is C