What wager does Pickering propose to Higgins?

In George Bernard Shaw's play "Pygmalion," Colonel Pickering proposes a wager to Professor Henry Higgins that he cannot transform Eliza Doolittle, a lower-class flower girl, into a refined lady who can pass for a duchess at an ambassador's ball in six months. Pickering bets that Higgins will not succeed, while Higgins confidently accepts the challenge, eager to prove his abilities in phonetics and social transformation. The wager sets the stage for the ensuing social experiment and character development throughout the play.