Biarritz need to beat Harlequins at home with a bonus and Northampton need to do similar in Glasgow. Tall order for both.
If Montpelier lose with a bonus against Toulon, and Toulouse do likewise against the Tigers, because of tries scored it means Munster and Leinster need a win bonus to get to stay ahead of them.
Then its down to tries and as things stand Munster are on 9 and Leinster on 8. So basically whatever Leinster do in Exeter, Munster have to mirror against Racing. That includes winning of course.