Puzzle of the week #319

Chess Diagram: 

[Event "Puzzle #319"][Date "2017.05.23"][Result "1-0"][SetUp "1"][FEN "2b2r1k/1p2Npbp/1n1Q2p1/1P6/1P3P2/1q4PP/5KB1/2R1R3 w - - 0 1"]

White is up and exchange and a pawn. He could have captured Nb6 with his next move but after analysing the position, he chose not to. Your tasks:
a) Show what was white afraid of if he would have captured the Knight with 1. Qxb6 ...
b) White could have captured the Knight anyway; analyse the position and find out what he missed

Total available points for this puzzle is 20. The answers will be published next time together with puzzle #320.

Puzzle #318 solution:
Study by L. Centurini. The nicest explanation was by Bradley:
"The trick black can use is to play Bd8 if white plays e7. That way if white plays e8=Q? or e8=R?, black is stalemated. This trick works because the black king is trapped by whites bishop and king, and the bishop gets pinned. Also, blacks king should go into the corner to try and get stalemated."

[Event "Puzzle #318"][Date "2017.05.17"][Result "1-0"][SetUp "1"][FEN "2k5/8/2K1P3/b7/8/6B1/8/8 w - - 0 1"]1. e7 Bd8 2. e8=B (2. e8=N Be7 3. Bc7 Bb4 4. Nf6 Ba3 5. Nd5 Bc5 6. Kxc5 {Jalen, Benjamin}) 2... Bc7 3. Bd7+ Kb8 4. Bxc7+ Ka7 5. Bc8 Ka8 6. Bd6 Ka7 7. Kc7 Ka8 8. Bb7+ Ka7 9. Bc5# {Bradley, Jalen, Boenjamin, Coco, Cody}

Correct solutions:
Jalen, Benjamin - 25 points
Bradley, Cody, Coco - 16 points
Dheera - 2 points

Jalen - 240 points
Coco - 212 points
Cody - 210 points
Bradley - 206 points
Benjamin - 127 point
Deryk - 107 points
Uros - 63 points
Dheera - 41 points
Yakov - 39 points