[6 points] Do a line-by-line analysis to find the running time of the fragment given in the following algorithm. Assume that the cost of the statement in line (i) is ci for i=1,2,3,4. sum = begin algorithm (1) 0; (2) for (i=log n; i>=1; i--) (3) for (j=n; j>1;j/=2) (4) sum+=array[i][j]; end algorithm