Answer: Reward power
Explanation:
The reward power is basically refers to the power of the manager that gives the promotion, appraisals and incentive to the employees in the organization. The reward power is the one of the type of power in an organization which helps to motivate the employees.
According to the question, the Ruben suggested her employee Eileen that if she keeps going good work in an organization then next year he give her reward power in the form of promotion.
The main advantage of the reward power is that it also influence the other employee for ding good work and also it motivate the employees.