P(echt | Z) = (9/10 * 0.5) / (9/10 * 0.5 + 1/10 * 1) = 9/11 = 81.82%
P(echt | ZZ) = (9/10 * 0.5^2) / (9/10 * 0.5^2 + 1/10 * 1^2) = 9/13 = 69.23%
P(echt | ZZZ) = (9/10 * 0.5^3) / (9/10 * 0.5^3 + 1/10 * 1^3) = 9/17 = 52.94%
P(echt | ZZZK) = (9/10 * 0.5^3 * 0.5) / (9/10 * 0.5^3 * 0.5 + 1/10 * 1^3 * 0) = 1 = 100%