So if Sparse Indexing is Used the Answer Should Be :-
Record Size = 100B
Block Size is = 1024B
Number of records in a block = 1024/100 = 10
Total blocks required = 30000/10 = 3000.
Now index Content = (Attribute,Block Pointer) = 9 + 6 = 15B
In 1024 Size Block = 1024/15 = 68.
So number of Blocks in 1st level = 3000/68 = 45.