IDENTIFY and EXPLAIN one internal control procedure that would be most effective in preventing the following errors or fraudulent acts?

a) An inadvertent data entry error caused an employee's wage rate to be overstated in the payroll master file.

b) A fictitious employee payroll record was added to the payroll master file.

c) During data entry, the hours worked on an employee's time card for one day were accidentally entered as 80 hours, instead of 8 hours.