4. Indicate whether, after both parties sign a closing agreement, the following result(s) occur. More than one answer may be correct.

a. The taxpayer still may appeal to a higher level of the IRS.

b. The interest on the assessment stops accruing immediately.

c. The agreement is binding on both the taxpayer and the IRS.

d. The tax must be paid, but a suit for refund can be filed in the District Court or U.S. Court of Federal Claims.