Primary duty typically means the duty that constitutes the major part (over 50 percent) of an employee's work. A duty constituting less than 50 percent of an employee's work (alternative primary duty) may be credited as the primary duty for exemption purposes provided that duty:
(1) Constitutes a substantial, regular part of the work assigned and performed;
(2) Is the reason for the existence of the position; and
(3) Is clearly exempt work in terms of the basic nature of the work, the frequency with which the employee must exercise discretion and independent judgment as discussed in § 551.206, and the significance of the decisions made.