3. Here is data from the Worldwatch Institute, showing the concentration of carbon dioxide in the earth's atmosphere, measured in parts per million (ppm) over a 20-year period: Year 1975 1976 1977 1978 1979 1980 1981 CO2 (ppm) 331.0 332.0 333.7 335.3 336.7 338.5 339.8 Year 1982 1983 1984 1985 1986 1987 1988 CO2 (ppm) 341.0 342.6 344.3 345.7 347.0 348.8 351.4 Year 1989 1990 1991 1992 1993 1994 1995 CO2 (ppm) 352.7 354.0 355.5 356.2 357.0 358.8 360.7 (a) What kind of model would you use to represent this with a function? Why? [APP: 2) (b) Find a function which models the data the best you can. [APP: 4] (c) Use your equation to estimate the concentration of CO2 in 2020. [APP: 2