Write SQL query to solve given problem: Mention the series code of countries using Australian dollar as their currency unit. Which country belongs to middle income group among them.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T1.CountryCode, T2.SeriesCode FROM Country AS T1 INNER JOIN CountryNotes AS T2 ON T1.CountryCode = T2.Countrycode WHERE T1.CurrencyUnit = 'Australian dollar' AND T1.IncomeGroup = 'Lower middle income'