Having a question about SQL

Consider the relations: EMPLOYEE(ID, SURNAME, LINE_ID) CAR(EID, MAKE) For each employee, we store their unique ID and the ID of their line manager (if exists) LINE_ID. If an employee has a line manager then the corresponding LINE_ID is not NULL. A line manager does not have a line manager, i.e., the corresponding LINE_ID is NULL. The LINE_ID is a foreign key referencing to the ID primary key in the relation Employee. In the relation Car, we store the car(s) make of an employee, if exist(s). Specifically, for each car, we store its make (e.g., BMW, Jaguar, Aston Martin, Toyota) and the ID of its owner/employee (EID). The EID is a foreign key referencing to the ID in the relation Employee. The primary keys are underlined. Assume the following query: SELECT E.SURNAME, L.SURNAME FROM EMPLOYEE E, EMPLOYEE L, CAR C WHERE E.LINE_ID = L.ID AND C.EID = L.ID We know that: (i) there are 20 line managers, each one being the line manager of 10 employees; (ii) there are 120 employees, who have 1 car each, i.e., the CAR relation has 120 tuples, each one corresponds to different employee. (a) Provide the canonical tree of the query and estimate the expected number of tuples retrieved.