Let present population ( P_5 = 4084101 ) and population 5 years ago ( P_0 = 3200000 ).
[ P_5 = P_0 \cdot r^5 \implies 4084101 = 3200000 \cdot r^5 \implies r^5 = \frac{4084101}{3200000} = 1.2762815625. ]
[ r = (1.2762815625)^{1/5}. ]
Taking fifth root (or successive roots): [ r \approx 1.05. ]
Rate of increase ( = (r-1)\times 100% = 5% ).
Answer: 5% per annum