ou are involved in a study of sickle cell anemia. In this disease, some red blood cells are "sickled" and behave abnormally. You are to determine the number of normal and sickled red blood cells per unit volume in a particular tissue. The volume of the tissue under examination is exactly 0.3 mm³. During a given period, you determine that there are 400,000 50,000 normal red blood cells (mean standard deviation) and 45,000 10,000 sickled red blood cells in the tissue. Find the mean standard deviation of the total number of red blood cells (normal + sickled) per unit volume in the tissue.