sizeof(arr) = 8, arr is just a pointer
sizeof(arr[0]) = 3 * sizeof(int)
&arr is undefined because we don't know where arr's adress is saved (just where arr begins)
arr is 400, because arr is a pointer whose address we know.
arr[0] because arr is a pointer whose address we know
arr[7][3] is undefined because we don't know where arr[7] is pointing at
&arr[7][3] - &arr[0][0] - there are 24 cells between them
&arr[8] - arr is the important thing is that &arr[0]=arr, therefore &arr[8]=arr+8