Concept: The question tests on the area of Modern Math (Counting/Combinatorics)

Solution:

Since books are a finite quantity, they have to be integers and they cannot be negative.

Statement 1: p3>j2

If p = 2 and j = 1, Then 2^3>1^2 and therefore p > j

If p = 5 and j = 11, Then 5^3>11^2 but p < j
Answer options could be B, C or E (Insufficient)
 

Statement 2: j = 3
Answer options could be C or E (Insufficient)

Combining both statements

 p3>j2 and j = 3. So p3>9

for this p has to be greater than 3 as cubes of 1 and 2 are less than 9.

Both the statements together are sufficient.
(Option C)