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-- this is my answer:

1) For all x, if there is no y on the x, then clear the x. 2) For all y and x, there is imposible that if y is on the table,then the y is on the x. 4) For all X, if pick up the x, then if there exist gripping and clear x and x is on the table, then grip the x. --- 1. For all X, If Y that suppose to place on X doesn't exists, then X is clear.

2. For all blocks X and blocks Y, if Y is on table then there is not exist where Y is on X.

3. Block Y is not gripped, with the condition of the gripping is empty where Y is not in the gripping.

4. For all block X, if X is clear and on table then gripping X where X is pickup by the gripper.

5. Put down X, when hand is griping X that clear on the table.

6. For all X and all Y, situation X stack Y will cause X place on Y, gripping nothing and X is clear. Otherwise, X is gripping and remove from the top of Y, and Y will be clear.

7. Block X wil be unstaking Y if X is on Y and X is clear and gripping is empty when X is gripping and Y is clear.

8. For all X, all Y, and all Z, if Y is unstack on Z, hence X in on table.

9. Y is stack on Z when X is on the table.

Doubt by chieng:

2. Where is the negate? 3. <-> if not mistaken is 'If and only if' wo... ...