3-6. Two ointments (call themAand B) for a particular type of skin disorder are being tested. Ten percent of patients did not show any improvement after one week. Half of them used ointment A. If (under randomization) it was determined that 40% of the patients were assigned ointment A, find:

(a) The probability that a patient will not improve if he or she is assigned ointment A.

(b) The probability that the patient will improve, given that he/she was treated with ointment A.