Well, I think we need to define the meaning of "plummet" first. May be difficult to draw a line, but given the $75 or so price not long ago, I think $35 would probably low enough for 'plummet'. But $58 is only $15 or 20% so below the current price, and that much change is not unlikely, given that a good portion of oil price is just a somewhat artificial markup based on fear, war, and future uncertainties, like what if the US bombs Iran? Which given that imbecile administration, isn't entirely impossible.