A certified public accountant (CPA) has found that nine of ten company audits contain substantial errors. If the CPA audits a series of company accounts, what is the probability that the first account containing substantial errors: a) is the third one to be audited? b) will occur on or after the third audited account? c) What is the average number of accounts that must be examined to find the first one with substantial errors? d) What is the standard deviation of the number of accounts that must be examined to find the first one with substantial errors