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Consider the relation enrolled (student, course) in which (student, course) is the primary key, and the relation paid (student, amount) where student is the primary key. Assume no null values and no foreign keys or integrity constraints. Assume that amounts 6000, 7000, 8000, 9000 and 10000 were each paid by 20% of the students. Considet these query plans (Plan 1 on left, Plan 2 on right) to “list all courses taken by students who have paid more than x,”
A disk seek takes 4 ms, disk data transfer bandwidth is 300 MB/s and checking a tuple to see it amount is greater than x takes 10 µs. Which of the following statements is correct?