(1 point) The table below gives U.S. lead emissions, L, into the environment in millions of metric tons for 1970-1992. Let t = 0 in 1970. Year 1970 1975 1980 1985 1988 1989 1990 1991 1992 Lead emissions 253 113.7 43.4 15.7 8.6 6 8 6 6.7 5.2 4.4 (a) Find an exponential model for these data. Lead emission, L(t) = 253(0.85)^t (b) Find a fourth-degree polynomial model for these data. Lead emission, L(t) = (c) Which of these curves gives a better model for the data? A. exponential model B. fourth-degree polynomial (d) Estimate the lead emission in 1983 according to the polynomial model in part (b).