A new vaccine is developed to fight the dread disease Q. Patients are recruited to participate in a clinical trial to see if the vaccine is safe and effective. Pa- tients are assigned alternately into the control arm (placebo) or the treatment arm (new vaccine) of the trial, and their outcomes are assumed independent. The probability of an adverse outcome is po for the control arm and p for the treatment arm. If the first patient is assigned to the control arm, what is the probability that the first adverse event occurs on the control arm?