Landlord and Tenant entered into a three-year written lease for office space at $1,000 per month. The lease provides that "if Tenant vacates the premises early, then Tenant shall be liable for the entire unpaid balance of the lease immediately." Tenant did, in fact, vacate the office after only one year, and Landlord sued, seeking recovery of $24,000.

What is Tenant's best argument that the Landlord should NOT recover $24,000 as provided in the contract?