14.4 Let an AND/OR graph be defined by: a ---> or:[b/1,c/2]. b> and:[d/1,e/1]. c> and:[e/1,f/1]. d ---> or:[h/6]. e ---> or:[h/2]. f ---> or:[h/4,i/2]. goal(h). goal(i). Draw all the solution trees and calculate their costs. Suppose this graph is searched by the AO* algorithm, where the start node is

a, and the heuristic h-values of the nodes

b, d,

e, h and i are all 0. Give the intervals for the values h

(c) and h

(f) that allow AO* to find the optimal solution.