How are red blood cell levels and hemoglobin levels related?

1. An increase in red blood cells and hemoglobin will decrease iron.
2. Anything that causes an increase or decrease in red blood cells will do the opposite to hemoglobin.
3. Anything that causes an increase or decrease in red blood cells will do the same to hemoglobin.
4. Anything that causes an increase or decrease in red blood cells will do the same to hemoglobin, but in much smaller amounts.