The formula to use is
A = P(1+r)^t
where,
A = final amount after t years
P = initial amount = 4100
r = rate of increase or decay = -3.75% = -3.75/100 = -0.0375
t = number of years = 11
The value of r is negative to indicate exponential decay. Also notice that I divided by 100 to convert from -3.75% to -0.0375
Using those values, we plug them into the formula to get,
A = P(1+r)^t
A = 4100(1+(-0.0375))^11
A = 4100(1-0.0375)^11
A = 4100(0.9625)^11
A = 4100*0.65676215615721
A = 2692.72484024457
A = 2693
Rounding to the nearest whole number, the answer is approximately 2693 km^2.