Pawn Promotion Endgame Problem-White to move and mate in 1 So I have not been this interested in chess for a very long time indeed. This problem was posed to me by someone who has recently become experienced in chess and also participated in a chess tournament, in which he did fairly well considering his level of experience.

[Title "White to move and mate in 1"]
[FEN "8/kPR5/5Q2/8/8/8/6B1/4K3 w - - 0 1"]


From my own deductions, the only possible way in which to even begin to solve the problem is with the move b7 to b8. However, I have yet to figure out how promoting the pawn can have an effect on the eventual outcome of the scenario, seeing as the black king can simply take whichever piece I decide to transform the pawn into.

The last hint I was given, by the person who posed to question to me, was that the relationship between the piece into which the pawn is transformed and the black king is paramount to the solution.

Please help me. All the chess engines I have tried using after an absurd amount of time, trying to figure it out by myself, and doing it with the help of others have failed me. 

All helpful tips/hints/advice/directions which may lead to the correct answer are welcome.
It's probably a trick problem with a promotion to a black knight.

Such promotions to the wrong colour are not allowed, and never were. In the official rules it is now specifically pointed out that the new piece has to have the same colour as the promoted pawn.

FIDE's laws of chess, Article 3.7 e:


  When a pawn reaches the rank furthest from its starting position it
  must be exchanged as part of the same move on the same square for a
  new queen, rook, bishop or knight of the same colour. The player’s
  choice is not restricted to pieces that have been captured previously.
  This exchange of a pawn for another piece is called ‘promotion’ and
  the effect of the new piece is immediate.