life-tree

I reach another node of the life-tree;
and,the question is:
how to estimate the profit of each subtree?
the algorithm is hard to be designed,since I can not have a try;
consequently,I need help;aha;yes,help.
aim to tackle this,I'm busy with sending and receiving letters these days;
but...darkness still on;
p.s.:what is the number of algorithms to estimate the value of a tree?
still now,details are still not explicit;
only several steps are confirmed:
one is enter-exam is given up;
another is what disciplines to review? discrete mathematics is important in glance;
buddies,a za a za fighting^_^