I couldn't resist. Sorry who is paying the prepayment? GXY have already sold all of 2017's production, at a market leading price (hint: no discount for prepayment). If there was going to be a prepayment it would've been negotiated with the sale and pricing, in my opinion, of course.
Perhaps your thinking 2018 production might be sold now, and you'll get a prepayment - not sure it would be a good idea for GXY, who may get a higher price closer to the event.
GXY Price at posting:
59.5¢ Sentiment: Hold Disclosure: Held