program alex;
const t=1000000007;
var f:text;
    viz:array[0..100001]of longint;
    nr,a:int64;
    i,n,k,x,y,j:longint;
begin
assign(f,'colorare3.in');reset(f);
readln(f,n,k);
for i:=1 to n-1 do
    begin
    readln(f,x,y);
    if x<y then inc(viz[x])
           else inc(viz[y]);

    end;
nr:=1;
 for i:=k downto k-viz[1]+1 do
     nr:=(nr*i)mod t;
for i:=2 to n do
    begin
    if viz[i]<>0 then begin
                      a:=1;
                      for j:=k-1 downto k-viz[i] do
                          a:=(a*j)mod t;
                      nr:=(nr*a)mod t;
                      end;

    end;
assign(f,'colorare3.out');rewrite(f);
writeln(f,nr);
close(f);
end.