Puzzle of the week #182

Level: 
4-Rook
Chess Diagram: 

[Event "Puzzle #182"][Date "2012.01.31"][Result "1/2-1/2"][SetUp "1"][FEN "8/8/8/p6p/P4K1P/8/4k3/8 b - - 0 1"]

You have to find the right idea and then stick with it until everything is clear cut. Do you like this explanation? Short and sweet, it does not need much more added to it except a couple of small important details:
a) Black to move; can he save the game?
b) Explain your solution

Good luck! Total available points for this puzzle is 20. The answers will be published next week together with puzzle #183.

Puzzle #181 solution:
Endgame by Grandpatzer (USA), 2009. Unfortunately only Ziyao got the solution from beginning to end. My only advice is when something does not make sense (such as question "a"), leave it for a while and then read it again carefully. Most of the times it will give you a better chance of finding what was not clear. Please try it in future! The solution by Ziyao:

[Event "Puzzle #181"][Date "2012.01.24"][Result "0-1"][SetUp "1"][FEN "8/8/2p5/1p1p4/p2Pk3/P1P5/4K3/8 w - - 0 49"]49.Kd2!? Kf4? {Answer to (a)} (49...b4 {Answer to (b)} 50.axb4 (50.cxb4 Kxd4 51.Kc2 Kc4 52.Kb2 d4 {Black wins}) 50...a3 51.Kc2 a2 52.Kb2 Kd3 53.Kxa2 (53.c4 dxc4 54.d5 cxd5 55.b5 c3+ 56.Kxa2 c2 57.Kb2 Kd2 {Black wins}) (53.Ka1 Kxc3 54.b5 cxb5 {Black wins}) 53...Kxc3 54.Ka3 Kxd4 55.Kb3 Kd3 {Gaining opposition and will eventually win when White moves to the side and Black makes way for his d-pawn to promote}) 50.Ke2 Kg4? 51.Kf2 Kf4? 52.Ke2 {A player with a poor knowledge of the endgames would agree to a draw here}

Correct solutions:
Ziyao - 20 points
Leo, Philip, Coco, Derrick, James, Harmony - 10 points
Daniel, Alex - 1 point

Standings:
Philip - 59 points
James - 51 points
Ziyao - 49 points
Jeffrey - 46 points
Harmony - 39 points
Alex - 33 points
Daniel - 30 points
Leo, Coco - 28 points
Derrick - 24 points
Leroy - 12 points

Comment: 

Basic endgame (2)