a has 4 descendants and 0 ancestors
b has 6 descendants and 0 ancestors
c has 2 descendants and 2 ancestors
d has 0 descendants and 2 ancestors
e has 1 descendants and 2 ancestors
f has 3 descendants and 0 ancestors
g has 0 descendants and 4 ancestors
h has 0 descendants and 4 ancestors
i has 0 descendants and 4 ancestors
j has 2 descendants and 0 ancestors