Hello!
The answer is:

Why?
We can calculate the area of the lake after 13 years using the following equation:

Where,
A(t), is the area after t time (years)
A(Initial), is the initial area
Shrinking Rate, is the rafe of shrinking and it's 6% or 0.06.
t, is the time
So, substituting we have:

So, the are after 13 years will be:

Have a nice day!