In addition to the basic salary of a unit of employees, a large part of their income comes from performance wages. In April this year, the performance wages of all employees in the first project group of the unit were higher than the highest performance wages of the second group of employees. The employee with the highest monthly performance salary is not in the first project group. From this we can infer:. ['The unit leader has the highest performance salary.', 'The performance salary of some employees in other project groups of the unit is not the first, and the average of the second project group is high.', 'Some employees of this unit do not belong to the first project team or the second project team.', 'The average performance salary of the second project group is lower than the average performance salary of the unit.']