19/32

THINK ALL PROB THAT B DOESN'T GET WATER:
4 SITUATIONS:
#1, NONE OF p2 p3 WORKS, PROB=1/4;
#2 P2 WORKS BUTP3 DOESN'T.PROB=1/4
THEN WE NEED P1 & P5 TO BE REST 1/4
SO, #2 OVERALL PROB=1/4*1/4;
#3, P2 DOESN'T BUT P3 WORKS, SAME THING AS #2,
WE NEED P4 AND P5 DON'T WORK.
OVERALL, 1/16;
#4 BOTH P2 AD P3 WORKS FINE(PROB=1/4),
THEN WE NEED ALL OF p1 p4 AND p5 REST(1/8).
SO OVERALL FOR #4: 1/32


FINALIZE:
PROB(B GET WATER)=1-(B DOESN'T GET WATER)=1-(#1+#2+#3+#4)
=1-(1/4 + 1/16 + 1/16 + 1/32)=1- 13/32= 19/32