We can't give you legal advice for 2 reasons: we aren't licensed to practice law in AZ, and we haven't read your lease.
If your lease says that you got a special rate for signing a 1 year lease and that you owe tha difference if you leave early, then you'll have to convince a judge that $1200 is an unconscionable amount of liquidated damages when the apt was empty for 2 weeks & they obviously didn't have any trouble re-renting it. You may not even have to reimburse them for advertising/showing the place, since they would have had to do that in a month anyway.
If the landlord's just trying to collect full rent from you for the entire lease period, he's SOL. Landlords can't collect rent on one apt from 2 tenants. The tenant who is not living in the apt can sue the landlord for 'unjust enrichment'. Again, L's damages are limited to what L can prove -- the per diem rent L didn't collect because you only paid until the 10th & he didn't re-rent until the 24th. Again, you argue that the advertising costs are not damages, since L would have incurred them anyway & L now has a new year lease.
Good luck & read your landlord tenant law.
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This is not legal advice and you are not my client. Double check everything with your own attorney and your state's laws.