Is It Ethical To Pay Radio Presenters To Air Songs. If So How Much, How Often?

Hi every one! Happy New Yr.  There's something I've been wondering about.  when promoting a new song of a new artiste on radio, is it ethical to give the presenters money?  If so, how much should one reasonably give the presenters, and how often?

My friend and i argued over this topic some time back. he's a budding artiste, and i'd like to hear from my fellow Nairalanders.