+a0 p3 p1 p4 p1 (1-p) p1 +(1-a0-a1) p2 p1 (1-p) p1 +a0 p3 p1 p4 p1 (1-p) (1-p1) +(1-a0-a1) p2 p1 (1-p) (1-p1)