It is a B+ tree. So at leaf level, there will only be record pointers. Assuming that there are 11 record pointers per block in leaf level, we will have 11*x = 1250, x = cel(113.64) = 114 blocks
It is given that there are 3 records per block, therefore number of blocks in leaf level = ceil(1250/3) = 417
To index these 417 blocks, we need ceil(417/11) = 40 blocks (Since there are 11 pointers per block)
Again, in next level we need ceil(40/11) = 4 blocks
Again, for those 4 blocks, we need 1 blocks.
Hence, a total of 4 levels.