Questions

Sum of all numbers in each row and columns must be 15.

In last row to gt sum as 15 missing number must replaced by 1. 

Fragmentation occurs in a dynamic memory allocation system when many of the free blocks are too small to satisfy any request. 

External Fragmentation: External Fragmentation happens when a dynamic memory allocation algorithm allocates some memory and a small piece is left over that cannot be effectively used. If too much external fragmentation occurs, the amount of usable memory is drastically reduced. Total memory space exists to satisfy a request, but it is not contiguous. 

Internal Fragmentation: Internal fragmentation is the space wasted inside of allocated memory blocks because of restriction on the allowed sizes of allocated blocks. Allocated memory may be slightly larger than requested memory; this size difference is memory internal to a partition, but not being used

It is very hard to catch breathe when you run fast.