THE UNITED AFRICA CO. LTD VRS PAUL JAZZAR AS SURETY FOR JOHN NAOUM-DECEASED  Since the surety knew that a debit balance was an ordinary in, of the relations between Respondents and principal debtor, and could ascertained the amount if he wished, he cannot be heard to complain Respondents that he did not know that their produce buyer had been overdrawing  his account or what the nature of his business was.