Answers:
(a) the population function is exponential in the number of years (t) after 2017:
(b) Although the model is defined on a yearly basis, we can answer the question by calculating the projected population at the end of 2018 (t=1) and, under the assumption of same birth rate every month, take half of the yearly increase (end of June):
N(1) = 29890.50
June population:
(c) N(1) = 29891 (see (b) above)
(d) Population in 2025 is the function value at t=2025-2017=8