They are asking size of the file. That means all we need to calculate is number of blocks*size of block to know the size of file. since files are being stored as blocks.
To calculate total number of blocks
Block size =1024 bytes
1)Directly given blocks 10*1024 bytes
2)single indirect block 1*128*1024 bytes (since 1 block is pointing to a block which has 128 address of 128 blocks each of size 1024. since it is given each block will have address of 128 other blocks
3)double, triple indirects with same logics
totally adding them gives total block sizes