When an employer does not have a sophisticated time-keeping system, it is valid to accrue a percentage of wages at end-of-period based on: a. it is never valid to estimate an end-of-period adjustment. b. a percentage based on previous period's payroll (for example, 4 out of 5 days = 80% x prior payroll). c. a percentage suggested by the IRS. d. a percentage that external auditors provide the payroll clerk