We have a dataframe df$,$ with columns $$col$1$ and $$col$2.$ Column $$col$1$ has a NaN value $($See Out$[2]).$ After we attempt to fill the NaN with the mean from the column $($In$[3]),$ what would the value in the NaN place be$?$

$0\mathrm{.}0$

$2\mathrm{.}0$

$1\mathrm{.}5$

$0\mathrm{.}5$