Answer: the function N(t) to estimate the level of contamination in the lake is:
N(t) = -1110 ln(t) - 230t + 1110 ln(I) + 230I + 5380
Step-by-step explanation: ∫ dN/dt dt = ∫ (-1110/t² -230) dt
N(t) = -1110 ln(t) - 230t + C
N(I) = -1110 ln(I) - 230I + C = 5380
C = 1110 ln(I) + 230I + 5380