Q69

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. Consider 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 $4ms,$ disk data transfer bandwidth is $300$ MB/s and checking a tuple to see if amount is greater than $x$ takes $10µs.$ Which of the following statements is correct?