Jay signed a two-year lease containing a clause that expressly prohibited subletting. After six months, Jay asked the landlord for permission to sublet the apartment for one year. The landlord...

Jay signed a two-year lease containing a clause that expressly prohibited subletting. After six months, Jay asked the landlord for permission to sublet the apartment for one year. The landlord refused. This angered Jay, and he immediately assigned his right under the lease to Kay. Kay was a distinguished gentleman, and Jay knew that everyone would consider him a desirable tenant. Explain whether Jay’s assignment of his lease to Kay is valid.