Four foreign business students rented the apartment of Thea for a period of one year. After one semester, three of them returned to their home country and the fourth transferred to a boarding house. Thea discovered that they left unpaid telephone bills in the total amount of P80,000.00. The lease contract provided that the lessees shall pay for the telephone services in the leased premises. Thea demanded that the fourth student pay the entire amount of the unpaid telephone bills, but the latter is willing to pay only one fourth of it. Who is correct? Why?