some accounting firms give the client an option to pay a fee when the tax return is completed that guarantees tax advices and support from the accountant if the client were audited. a large accounting firm is trying to determine what the fee charge for next years return. in previous years the actual mean cost of the firm for attending a client audit session was $720. to determine if the cost has changed, the firm randomly samples 37 client audit fee.the sample mean audit cost was $690 with standard deviation of $75.complete parts a and b below. Develop a 90% confidence intervals estimate for the mean audit cost.