Foreign Adoptions. The number of foreign adoptions in the United States has declined in recent years, as shown in the table below.
Year, x Number of U.S. Foreign Adoptions from Top 15 Countries, y
2000, 0............................. 18,120
2001, 1............................. 19,087
2002, 2............................. 20,100
2003, 3............................. 21,320
2004, 4............................. 22,911
2005, 5............................. 22,710
2006, 6............................. 20,705
2007, 7............................. 19,741
2008, 8............................. 17,229
2009, 9............................. 12,782

a) Use a graphing calculator to fit quadratic, cubic, and quartic functions to the data. Let x represent the number of years since 2000. Using R2-values, determine which function is the best fit.
b) Using the function found in part (a), estimate the number of U.S. foreign adoptions in 2010.