$1-$ Make a new dataframe by selecting only columns C $($Plant state abbreviation$),$ S $($Unit unadjusted annual SO$2$ emissions $($tons$)),$ T $($Unit unadjusted annual CO$2$ emissions $($tons$)),$ and U $($Unit unadjusted annual Hg emissions $($lbs$))$ from the sheet UNT$20.$

$2-$ Using the new dataframe, transform the data format to numeric. Remember you need to transform all three numeric columns.

$3-$ Using the dataset from step $2-$ Change the column header names as follow: Col$1-$ Change to State; Col$2-$ Change to SO$2$; Col$3-$ Change to CO$2$; Col$4-$ Change to Hg$.$

$3-$ Filter the table by removing anything that is not a State name.

$4-$ Group the data by State

$5-$ Summarize the SO$2$ column by mean.