Compute the monthly mean wind speeds for all the three airports.

There is one obvious outlier amongst the observed wind speeds. Locate it $($programmatically$,$ do

not hardcode the date$/$day$/$row number$)$ and replace it with np$.$nan $($NaN$)$ before computing the

means.

$6.$ Draw the monthly mean wind speeds for the three airports on the same plot $($three curves of different colours$).$ Add a readable legend. Reference result: