I don't know if this is helpful at all and it isn't in relation to maths, but one of my friends received an 'N' for Unit 1 of Psychology this year. He was given an extension before failing and I think two days before the work was due the teacher reminded him, stating that she couldn't push the due date back any further. At one point during that conversation, this exchange was had:
'Do you know what happens if you don't hand it in?' - Teacher
'I'll be kicked out of the class?' - Friend
'No, you'll just get an 'N' for this unit.' - Teacher
He proceeded to not hand in the task (automatically earning a 0), got an 'N', and is still in the class doing fine.
All that to say, I think you'll be fine failing Unit 1, I can't see a reason they wouldn't let you continue unless your school is a lot more strict than mine.
I hope that somehow helped.
~ Kisses!
