Here total 5000 records and each block can take at most 10 records So.
No of block in the for relation will be = 5000/10 => 500
No of block is required for 1st level index will be 500/15 => 33.33 which will be 34
#block at second level = 34/15 => 2.26 => 3
#bloc at level 4 because in multi level index we try to put last index in one block but in upper case here 3 block are in use so ceil(3/15) => 1
So total #blocks will be 500+34+3 +1=538
This question i have calculated for dense Index.