Assume that RBCs live 100 days. How many must you make per second to keep your cell count constant?
You have to have the population to do this. Assume the number of RBC in the blood is P
Then the rate dying is P/100 days
Then the rate of regeneration must be the same.
So now, the question is how many seconds is in 100 days?
Rate= P/secondsin100days for number per second.