The table shows the total personal income in the United States (in billions of dollars) for selected years from 1960 and projected to 2024. Year Income ($ billions) Year Income ($ billions) 1960 411.5 2008 12,100.7. 1970 838.8 2014 14,728.6 1980 2307.9 2018 19,129.6 1990 4878.6 2024 22,685.1 2000 8429.7 (a) These data can be modeled by an exponential function. Write the equation of this function, with x as the number of years past 1960 and y as the total personal income in billiom (Round your numerical values to three decimal places.) y= (b) Does the unrounded model overestimate or underestimate the total personal income given in the table for 2018? The model overestimates the projected total. The model underestimates the projected total. (c) Graphically determine the year the model predicts total personal income will reach $63 trillion.