Please explain

Blood types: The blood type 0 negative is caled the. 'universal donor" type, because it is the onIy blood type that may safely be. transfused into any person.'Therefore, when someone needs a transfusion in an-ernergency and their blood type cannot be determined, they are given type-O negaljve blood. For this reason, donors with this blood type are crucial to blood banks. Unfortunatay, this blood type is fairly rare; according to the Red Cross, only 7% of U.S. redents have typei negative blood. Assume that a blood bank' has recruited 19 donors. [a] 1What is the mean number of donors who have type 0 negative blood? Round the answer to two decimal places. The mean number of donors who have type 0 negative blood is D . [b] What is the standard deviation of the number of donors who have type-D negative blood? Round the answer to four decimal places. The standard deviation of the number of donors who have type 0 negative blood is D