1 Figure 4 shows a blocks-world problem that is known as the Sussman anomaly. The problem was considered anomalous because the noninterleaved planners of the early 1970s could not solve it. Write a definition of the problem and solve it, either by hand or with a planning program.

A noninterleaved planner is a planner that, when given two subgoals G1 and G2, produces either a plan for G1 concatenated with a plan for G2, or vice versa. Explain why a noninterleaved planner cannot solve this problem.