For a time series data set with $100$ observations. hat$({)}_2=1\mathrm{.}76440,$ hat$({)}_5=0\mathrm{.}85559$ and $r_2=0\mathrm{.}62805.$ Then $r_5=$

For an approximation of the standard error of $r_5$ if the time series is white noise, we have $se(r_5)$~$=$