Last month Tim purchased $$20,000$ of U$.$S$.$ Treasury bonds $($their face value was $$10,000).$ These bonds have a $25-$year maturity period, and they pay $1\mathrm{.}5\%$ interest every three months $($i$.$e$.,$ the APR is $6\%,$ and Tim receives a check for $$300$ every three months$).$ But interest rates for similar securities have