The world population at the beginning of 1980 was 4.5 billion. Assuming that the population continued to grow at the rate of approximately 2%/year, find a function Q that expresses the world population (in billions) as a function of time t (in years). (Let t = 0 represent 1980 where t is years since 1980.)
What does Q(t) = and what will the world population be at the beginning of 2019 ?