Puzzle of the week #349

Queen versus pawn endgames are easy if you understood what needs to be done each time. This is a good test of how well you know them. Please setup the position needed in each case to answer correctly. Your tasks:
a) White has Kb7, Qd8. Black has Kb2, a2-pawn. What is the result of this endgame? Explain why
b) White has Kb5, Qd8. Black has Kb2, a2-pawn. What is the result of this endgame? Explain why
c) White has Kb7, Qd8. Black has Kb2, c2-pawn. What is the result of this endgame? Explain why
d) White has Kb5, Qd8. Black has Kb2, c2-pawn. What is the result of this endgame? Explain why
Knowing the result for each endgame gets you 5 points. The right explanation gets you 10 points each time.
Total available points for this puzzle is 60. The answers will be published next time together with puzzle #350.

Puzzle #348 solution:
Basic endgames, Lisitzin. This week's best answers are by Aiden and Matthew:
a) The white King is close to the black King and pawn
[Event "Puzzle #348"][Date "2018.05.20"][Result "1-0"][SetUp "1"][FEN "2Q5/8/8/8/8/8/4p2K/5k2 w - - 0 1"]1. Qc4 Kf2 2. Qf4+ Ke1 3. Qd4 Kf1 4. Qg1#

Correct solutions:
Aiden, Matthew - 15 points
Mengbai, Lyvia - 10 points
Jacey, Eric - 7 points
Walter, Coby, Brian, Joey, Glyn, Zhengyu - 6 points
Itamar, Chris, Lucas - 3 points

Standings:
Matthew - 96 points
Lyvia - 89 points
Joey - 88 points
Aiden - 86 points
Coby, Eric - 81 points
Walter, Zhengyu - 74 points
Mengbai - 56 points
Glyn - 51 points
Blake - 46 points
Brian - 44 points
Lucas - 37 points
Jacey - 31 points
Itamar - 18 points
Steven - 14 points
Chris - 10 points