Answer:
it should be 14,580 m^2
(the ^2 means squared btw)
the value of r of the geometric series n=11.3(0.8)n-1

General formula for nth term of any geometric series is 
Here 'r' is the common ratio
a_1 is the first term of the series
Now we compare the given formula with general formula
Compare
with 
The value of r= 0.8