Someone

fun sredniaa (rej) =
let
fun jakas(x,y,[]) = (x,y)
| jakas(x,y,(kA, (naz,cen))::rej) = jakas(cen+x,y+1.0,rej)
val (suma,ilosc) = jakas(0.0,0.0,rej);
in
suma/ilosc
end;

sredniaa (Rejestr);