In her second month of leasing her new apartment, the weather turns bitter cold and Amy discovers that the heating unit doesn't work. Amy is certain that she did not cause the damage. Amy's lease does include a Landlord's Covenant to Repair. If Amy asks her Landlord to repair or replace the heating unit, and Landlord refuses, What is Amy most likely permitted to do?
1) Terminate the lease on grounds of the apartment not being habitable
2) Stay in the apartment, pay the full rent, and sue the Landlord to force the repair
3) Start a fire in the middle of her apartment to stay warm
4) Refuse to pay rent until the heating unit is fixed
5) Replace the heating unit herself and then force the Landlord to reimburse her