State whether the following changes should be accounted for and, if so, whether retrospectively or prospectively, in accordance with IAS 8:
(a) A change in accounting policy made voluntarily.
(b) A change in accounting policy required by an accounting standard.
(c) A change in an accounting estimate.
(d) An immaterial error discovered in the current year, relating to a transaction recorded two years ago.
(e) A material error discovered in the current year, relating to a transaction recorded two years ago. Management determines that retrospective application would cause undue cost and effort.
(f) A change in accounting policy required by an accounting standard. Retrospective application of that standard would require assumptions about what management's intent would have been in the relevant period(s).