Puzzle #DI70C answer loses extra material. A whole rook worth 5 over a positive 4 point exchange.

Why is the 4 point exchange better?

lichess.org/training/DI70C

Black was two pawns down in the beginning. At the end of the solution, he has a queen for a rook and two pawns. In the process, he won "4 points" in material. Enough for the opponent to resign.

So not sure what you are counting here.

I think, it's about 39. Rd7+, where 39. Qxc2 wins a full rook, but apparently gives black a perpetual.

Yeah, maybe. Those things are easily checked by switching on the engine for a second.

i haven't seen engine but why to calculate if you can win easily by taking the queen...

@sheckley666 said in #3:
> I think, it's about 39. Rd7+, where 39. Qxc2 wins a full rook, but apparently gives black a perpetual.

Either that, or you get 39.Qxc2 d4+ 40.Kxf2 Rf3+ 41.Kg7 Rxf1+ 42.Kxf1 Qh1+ Ke2 42.Qg2+ Kd3 43.Qf3+ Kd4 44.Qf6+ winning the R.

As @nadjarostowa said: just turn the engine on and you can work all this out for yourself.