Main Sequence Fitting $(5$ pts$.)$

A bright A spectral star should have a luminosity or $102$ LSun $(3\mathrm{.}85$x$1028$ W$).$ The intensity measured at Earth

is rather faint, $10-15$ W$/$m$2.$ How far away is this star?

$($a$)$ About $1\mathrm{.}85$ billion ly

$($b$)$ About $185$ million ly

$($c$)$ About $18\mathrm{.}5$ million ly

$($d$)$ About $1\mathrm{.}85$ million ly

$($e$)$ About $185$ thousand ly