So in step six, what we basically want to do is we want to transform the gap molecule into one three BPG. Why? Well, because we want to transform a molecule that has a relatively low potential to transfer phosphoryl to a molecule that has a relatively high potential to transfer that phosphoryl group. And so we basically take the gap, we mix it with our NAD plus and we also use an orthophosphate. And in the presence of gap dehydrogenase, so dehydrogenase basically means we're going to have a reaction which there will be a transfer of a Hydride group. And so this will be reduced into NADH.