Puzzle of the week #40

Let's practice some more checkmates with a different piece than Queen and Rook. This position was composed by Selgiabkin back in 1984. What needs to be done:
a) White to move and mate in 5 (5 points)
b) What was different in this puzzle compared with puzzle #39 (2 points)?
Total available points for this puzzle is 7. The answers will be published next week together with puzzle #41.

Puzzle #39 solution:
This must be one of the most inspired weeks with no less than 10 solvers sending correct solutions. Mating with the pawn must be the icing on the cake. Please also note that all Black moves were forced. Without further ado here is the solution:
[Event "Puzzle #39"][Date "2008.10.02"][Result "1-0"][SetUp "1"][FEN "r4r2/pp1R4/6R1/2kbp3/B1p4p/2P1K3/PP5P/8 w - - 0 1"]1.b4+ cxb3 2.Rc7+ Bc6 3.Rcxc6+ bxc6 4.Rxc6+ Kd5 5.c4#

Correct solutions:
John, Jeremy, Karl, Wilson, Mark, Katerina, Joanne, Andy Q, Nathaniel and Joshua - 10 points
James - 1 point

Standings:
John - 35 points
Andy Q - 32 points
Jeremy and Joshua - 29 points
Katerina - 25 points
Joanne - 23 points
Karl - 21 points
Nathaniel - 18 point
Wilson - 15 points
Mark - 12 point
James - 3 points