Mistake in WashU Common App

I recently submitted my Common App (have not turned in the writing supplement yet) to WashU. I indicated an interest in Beyond Boundaries, but only after submitting realized that it changed my essay prompt. I already wrote an essay for the original prompt for WashU, and I really like my essay, so if there is any way for me to retract my interest in Beyond Boundaries and submit my original essay how should I go about doing this? That said, if retracting my interest in Beyond Boundaries gives me a bad first impression for the admissions officers, please let me know, because then I’ll just write the essay for Beyond Boundaries. Thanks!