Suppose I have a relation Grades(student_id, assignment_id, score). I have 200 students and 20 assignments. I would grade all submissions of one assignment based on the submission order, and then insert the records. As a result, based on my insertion nature, the student_id is not sorted, but the assignment_id is. I choose heap file as my file organization. My page is quite small it can only store 40 records, or 200 bytes in one page. The SearchKeySize is 2 bytes and PointerSize is 2 bytes. My buffer size is also small, 4 pages.

1. If my most frequent query is to find individual students, such as select * from grades where student_id=3347; select * from grades where student_id=8462;
   1. What is the I/O cost (i.e., number of pages in reading and writing) for finding one student if I dont build index for student_id? (note: student_id can appear as many as 20 times in this relation)

Note: Please explain the answer after answering.