Reducing subsetsum to $L = { langle G, l, urangle | G text{ is weighted tree that has a spanning tree with weight between $l$ and $u$}}$

How can i reduce Subsetsum (or maybe other np-complete problem) problem to the problem below ?

input : weighted tree $G$ and numbers $l$ and $u$. output : Does $G$ has spanning tree ,$S$, such that $l leq weight(S) leq u$ ?