total running time? Count the number of operations and what is the sum

Please do each one, they are really short, it is to help me understand how to trace code

int i, sum=0; for (i = 0; i < 3; i++) sum = sum + i;

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

int i, sum=0, prod=1; for (i = 1; i <= 3; i++) { sum = sum + i; prod = prod * i; }

int i, sum=0, prod=1; for (i = 1; i <= n; i++) { sum = sum + i; prod = prod * i; }

int i,j, sum=0; for (i = 1; i < 3; i++) for (j =1; j < 3; j++) sum = sum + i;

int i,j, sum=0; for (i = 1; i < n; i++) for (j =1; j < n; j++) sum = sum + i;