Equivalent employees means the number of employees computed by dividing the total hours paid in a year by the product of forty times the number of weeks in a year. Only the hours paid to employees who were employed in Nebraska and subject to the Nebraska income tax on compensation received from the taxpayer shall be included in such computation. A salaried employee who receives a predetermined amount of compensation each pay period on a weekly or less frequent basis is deemed to have been paid for forty hours per week during the pay period.