Puzzle of the week #118

Level: 
4-Rook
Chess Diagram: 

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---k----
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---K--B-
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P--R----
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Fisher is a name requiring no introduction. He has touched with his magic wand an entire generation of people (not only chess players) from all walks of life. Even today, 38 years after he won the World Championship title in convincing fashion, people know who he was. However very few still know that in the beginning (mid 60s) he wrote a series of chess articles in the magazine "Boy's Life". In those articles he challenged the readers (between other things) to solve extremely interesting chess puzzles. We would expect no less from him. Today Fisher appears yet again from the past and challenges you:
a) White to move and mate in 4;
b) Explain your solution

This time it is important to be accurate (cover all options) and efficient (win the fastest), two attributes Fisher was the best in the World at. You can be too, even if for only a week! Total available points for this puzzle is 20. The answers will be published next week together with puzzle #119.

Puzzle #117 solution:
Very good response from most of you. This has been an interesting example from a game between two very creative Grand Masters: Mamedyarov - Carlsen, Baku Grand Prix 2008. The solution is extremely surprising because of its simplicity. Who would expect it when the White Queen is pinned and forced to be exchanged, while very few pieces remain? Andy Y had one of the better answers:
"My guess would be
a) Resigned,
since the loss of a piece is inevitable for Black after 1... Kh7. In the diagrammed position, material is even (White has 3 pawns for a bishop). White's King is safer than Black's because it is not under attack. White also has 2 connected passed pawns on the d and e files. Overall, White has the advantage. This is best demonstrated with:
1.Ng6+ Kh7 2.Qxa8 Rxa8 3.Rf7 ... attacking the Knight on d7.
Moving the Knight hangs the bishop, and
3... Rd8 loses to
4.Rxd7 Rxd7 5.Nxf8+ Kg8 6.Nxd7 ... 1-0"

Correct solutions:
Jeffrey - 19 points
Andy Y, Karl - 18 points
Edwin, Owen - 16 points
Frank - 15 points
James, Alex - 10 points

STANDINGS

Owen - 338 points
Andy Y - 335 points
Karl - 318 points
Edwin - 291 points
Jeffrey - 241 points
Andy Q - 214 points
Alex - 207 points
James - 199 points
Humphrey - 180 points
Nathaniel - 136 points
Amir - 103 points
Frank - 20 points
Rick - 18 points
Marko - 10 points

Comment: 

Fischer challenge