program p1;
type strada=record i,j:integer;end;
var f,g:text;
    a:array[1..4000,1..4000] of shortint;
    b:array[1..4000] of shortint;
    i,n,m,k,x,y,j:longint;
    prod:int64;

begin
     assign(f,'colorare3.in');reset(f);
     assign(g,'colorare3.out');rewrite(g);

     read(f,n,k);

     for i:=1 to n-1 do
     begin
        read(f,x,y);
        a[x,y]:=1;a[y,x]:=1;
        b[x]:=b[x]+1;
        b[y]:=b[y]+1;
     end;
     for i:=1 to n do
     b[i]:=b[i]-1;
     prod:=1;
     for i:=1 to n do
     for j:=1 to n do
     if a[i,j]=1 then
     begin
          prod:=(prod*(k-b[i]-b[j]+1)) mod 1000000007;
          a[j,i]:=0;end;
     writeln(g,prod);
     close(f);
     close(g);
end.