The following data show estimates of the population of Liberia in selected years between 1960 and 2010:

Year	1960	1970	1980	1990	2000	2010
Population (millions)	1.1	1.4	1.9	2.1	2.8	4

Calculate the rate of growth of the population in millions per year for 2010.

(a) Use two-point backward difference formula.

(b) Use three-point backward difference formula.

(c) Using the slope in 2010 from part (b), apply the two-point central difference formula to extrapolate and predict the population in the year 2020.