Exemplo (União|Interseção)
zX = {a, b, c, d, e}
yA = {1/a, 0.7/b, 0.3/c, 0/d, 0.9/e}
yB = {0.2/a, 0.9/b, 0.4/c, 1/d, 0.4/e}
y
yC = {1/a, 0.9/b, 0.4/c, 1/d, 0.9/e}
yD = {0.2/a, 0.7/b, 0.3/c, 0/d, 0.4/e}