Right Of First Refusal Clause Vs Listed Property :: Who Wins?

[Jerome Harrod II]

Hey I'm really looking for some guidance here, did research beforehand, but I'm still not grasping the concept.

Here's the breakdown:

1. Investor talks to Seller about buying their house on a lease option.
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2. Seller tells Investor that the property is listed with an agent.
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3. Investor convinces Seller to allow him to buy said house with the "right of first refusal".

How does the new contract with the "right of first refusal" work around the existing agent's listing agreement? What happens to the agent in this case?

Furthermore, Can this be considered as an unethical practice?

Any input or opinion would be greatly appreciated.