The interest rate on U$.$S$.$ three$-$month Treasury bills dropped to very low levels at the end of $2008$ and remained there for several years. The table below contains data for four consecutive months from this period. The data are the three$-$month U$.$S$.$ Treasury bill rate, $R_{US}$; the Korean $91-$day Monetary Stabilization Bond interest rate, $R_{SK}$; and the exchange rate of the U$.$S$.$ dollar against the Korean won $($won per dollar$),E_{\frac{W}{\text{\$}}}.$

$\backslash$table$[[$Date$,R_{US},R_{SK},E_{\frac{W}{\text{\$}}}$