Answer: Substitutability
Explanation: Substitutability seems to be the limiting factor to Zena's power in getting a pay raise over her co-workers as it refers to the availability of alternatives. This is due to the fact that she is substitutable (capable of being used as a substitute or an alternative) as she is just one among the several other analysts with knowledge about municipal bonds which diminishes her power. Therefore, under the condition of substitutability, Zena's power cannot be translated into influence in her organization as it plays a role in determining the extent to which she can leverage the power she has to make things happen within the brokerage firm.