Give a reason for your answer. All x-coordinates at which f has a relative maximum. So you might say, oh, look, this looks like a relative maximum over here, but this isn't f, this is the graph of f prime. So let's think about what needs to, we don't have a graph of f in front of us. So let's think about what needs to be true for f to have a relative maximum at a point. So let's, we are probably familiar with what relative maxima look like. They look like a little lump like that.