Usual and customary line of employment is to be determined by evaluation of the following factors:
(1) The skills or abilities of the person;
(2) The length of time the person spent in the type of work engaged in at the time of the injury;
(3) The proportion of time the person has spent in the type of work engaged in at the time of injury when compared to the employee's entire working career; and
(4) The duties and responsibilities of the person at the workplace. It is not limited by the position held at the time of the injury.