What is the big-O of the following code fragment? int sum = 0; for(int i = 0; i = 0; j--) sum = sum +

What is the big-O of the following code fragment?

int sum = 0;

for(int i = 0; i <= n; i++)

for (int j = m ; j > = 0; j--)

sum = sum + (Math.pow(i,2) * Math.pow(j,2));