pressurised(p1).
pressurised(p2) <- on(t1) & pressurised(p1).
flow(shower) <- on(t2) & pressurised(p2).
wet(bath) <- flow(shower).
flow(d2) <- wet(bath) & unplugged(bath).
flow(d1) <- flow(d2).
on(t1).
on(t2).
unplugged(bath).
