The table shows the cost of a year's tuition, room and board, and fees at 4 -year public colleges for the years $2002-2010 .$ Letting $y$ represent the cost and $x$ the number of years since 2002 we find that the function $$f(x)=9318(1.06)^{x}$$ models the data quite well. According to this function, when will the cost in 2002 be doubled?
$$\begin{array}{c|c}\text { Year } & \text { Average Annual cost } \\\hline 2002 & \$ 9,119 \\
\hline 2003 & \$ 9,951 \\\hline 2004 & \$ 10,648 \\\hline 2005 & \$ 11,322 \\
\hline 2006 & \$ 11,929 \\\hline 2007 & \$ 12,698 \\\hline 2008 & \$ 13,467 \\
\hline 2009 & \$ 14,265 \\\hline 2010 & \$ 15,067 \\\hline\end{array}$$