Puzzle of the week #350

Chess Diagram: 

[Event "Puzzle #350"][Date "2018.06.02"][Result "1-0"][SetUp "1"][FEN "6RK/8/3k4/2p5/8/8/8/8 w - - 0 1"]

White has a Rook for a pawn material advantage in this endgame. It remembers that in order to win it needs to win the pawn, but does not remember how. Your tasks:
a) Find the winning line
b) Explain how you came up with it

Total available points for this puzzle is 30. The answers will be published next time together with puzzle #351.

Puzzle #349 solution:
Questions by Valer Eugen Demian, 2018. This week's best answers are by the top scorers:
a) White has Kb7, Qd8. Black has Kb2, a2-pawn
"The position is a draw because the black King can hide in the corner in front of the a2-pawn, threatening stalemate. The white King cannot come and help"
b) White has Kb5, Qd8. Black has Kb2, a2-pawn
"The position is a win. White will check from the side and then bring its King close. When black promotes, its Queen cannot stop the checkmate"
c) White has Kb7, Qd8. Black has Kb2, c2-pawn
"The position is a draw because the Queen cannot capture the c2-pawn. The black King goes in the corner and in case of capture, we have stalemate"
d) White has Kb5, Qd8. Black has Kb2, c2-pawn
"This was a trick question; the position is a draw like for question "c". It does not matter the white King is 2 rows closer"

Correct solutions:
Coby, Mengbai, Matthew, Eric - 60 points
Aiden - 55 points
Jacey - 41 points
Joey - 40 points
Blake, Lyvia - 36 points
Walter - 32 points
Zhengyu, Itamar - 26 points
Lucas - 22 points
Brian, Glyn - 18 points
Chris - 5 points

Blake - 3 points for puzzle #348

Matthew - 156 points
Aiden, Coby, Eric - 141 points
Joey - 128 points
Lyvia - 125 points
Mengbai - 116 points
Walter - 106 points
Zhengyu - 100 points
Blake - 85 points
Jacey - 72 points
Glyn - 69 points
Brian - 62 points
Lucas - 59 points
Itamar - 34 points
Chris - 15 points
Steven - 14 points


Rook versus pawn