since each page table must be contained within the page, so the size of each page table = 1024 bytes
let there are 'n' rows in page table and size of each row is 2 bytes
so
2*n=1024
n=512
that means there are 512 rows in a page table.
So bits required to represent each row = log2 512 = 9
Now virtual address is 64 bytes out of which 10 bytes are used for page offset
So bits used to represent page table = 64-10 = 54 bits
So lvl of page tables = 54/9 = 6
Hence answer should be 6