If nominal GDP increased by $8\%$ from $1963$ to $1964,$ what was nominal GDP in $1964?$ Round your answer to the nearest hundredth.

Year Nominal GDP $($in billions$)$

$1960$ $$540$

$1961$ $$561$

$1962$ $$606$

$1963$ $$639$

$1964?$

$1965?$

Provide your answer below: