a) White to mate in one.

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b) White to mate in two.

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c) White to mate in three.

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d) White to mate in three.

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Solutions:   a) R-e8 mate            b) R-e8, RxR   followed by  RxR mate    

                        c) Q-e8, RxQ  then  RxR, RxR   followed by RxR mate   

                        d) QxR, RxR   then R-e8ch, RxR  followed by RxR mate