Every person's blood type is A, B, AB, or O. In addition, each individual either has the Rhesus (Rh) factor (+) or does not (−). A medical technician records a person's blood type and Rh factor. List the sample space for this experiment. (Enter your answer in set notation. First list the blood type, and then the Rhesus factor, using P for positive (+), and N for negative (−). For instance, enter blood type A with Rhesus factor (+) as AP.)