Possessive Adjective Ihr declined

Hallo, I am trying to swot up my German grammar that I knew last year but have forgotten. So in my translation exercise one sentence says "Have you begun your work already?". And I wrote "Haben Sie [color=#0000FF:119a79r5]Ihre[/color:119a79r5] Arbeit schon begonnen?". But this is wrong; in the answer book is written "Haben Sie [color=#0000FF:119a79r5]Ihr[/color:119a79r5] Arbeit schon begonnen?". I cannot figure out why Ihr is correct, because in the dictionary Arbeit shows as feminine, and in the grammar book it seems the singular feminine accusative is Ihre. So what is the mysterious other rule that makes this Ihr and not Ihre? Please tell me if you know, because it is annoying me no end that I cannot figure this out. Many thanks to whoever solves the mystery!! Caroline

Hi there, I can understand that this is annoying you to no end. Well the good news is that you are right. Never underestimate your own skills. You know a lot and not all printed material is right. "Haben Sie Ihre Arbeit schon begonnen?" is correct. You mentioned all the right reasons why this has to be correct. There is no mystery to it, you have the answer to it already. Well done! Paul

Thank you for your quick reply. regards, Caroline