Solve the problem:

The number of inhabitants in millions of a certain city can be calculated using the expression [tex]p (x) = 2^{3} * 10\frac{2t}{3}[/tex] If t represents time in years:

a) How long approximately must elapse for the population of the city to be 200 million inhabitants?

b) How many inhabitants will be in the city after 4 years?