Concept:Consumer surplus is the extra benefit a consumer gets when he pays less than the maximum amount he was willing to pay.Explanation:The consumer planned to spend 120 kobo, so this is his maximum willingness to pay.He actually spent 80 kobo.Consumer surplus =120−80=40 kobo.Since 100 kobo =N1, then 40 kobo =N0.40.Answer:B. N0.40