Human blood may contain either or both of two antigens, a and b. blood that contains only the a antigen is called type a, blood that contains only the b antigen is called type b, blood that contains both antigens is called type ab, and blood that contains neither antigen is called type o. at a certain blood bank, 28% of the blood donors have type a blood, 15% have type b, and 10% have type ab. round the answers to two decimal places.