Real estate law

6. Upon an Assignment of an Apartment Lease by the original tenant ( " Original Tenant") and a subsequent default in the payment of rent, by the then tenant-in-possession (the "Assignee Tenant"), by law whom can the Landlord sue to collect the rent owed and whom must the Landlord sue to regain possession of the apartment? 7. Upon a Sublease of an Apartment Lease by the Original Tenant ( "Original Tenant"), and a subsequent default in the payment of rent, by the then tenant-in-possession ("Sublessee Tenant"), by law whom can the Landlord sue to collect the rent owed and whom must the Landlord sue to regain possession of the apartment