The table below lists the volume of nonfederal student loans, in billions of dollars, represented in terms of the number of years since 2004.
Year, x Volume of student Loans (in billions)
2004, 0 ................................. $15.1
2006, 2 ...................................20.5
2008, 4 ...................................11.0
a) Fit a quadratic function f 1x2 = ax2 + bx + c to the data, where x is the number of years since 2004.
b) Use the function to estimate the volume of nonfederal student loans in 2007.