P 1 = 1/4
P2 = (3/4) * (1/3) =1/4
P3 = 3/4 * 2/3 *1/2 =1/4
P4 = (3/4) * (2/3) * (1/2) =1/4
만족하세요, 받아주세요, 감사합니다!