#include <stdio.h>
#define NMAX 100005
#define MOD 1000000007
#define ll long long
int n,k,grd[NMAX];
ll pos[NMAX],rez,B[NMAX];
char viz[NMAX];
void read()
{
	scanf("%d%d",&n,&k);
	int i,x,y;
	for (i=1; i<n; i++)
	{
		scanf("%d%d",&x,&y);
		grd[x]++;
		grd[y]++;
	}
}
void precompute()
{
	int i;
	B[0]=1;
	for (i=1; i<=n; i++)
	{
		B[i]=B[i-1]*(k-i);
		if (B[i]>=MOD)
			B[i]%=MOD;
	}
}
ll aranj(int a,int b)
{
	int i;
	ll act=1;
	for (i=a-b+1; i<=a; i++)
	{
		act*=i;
		if (act>=MOD)
			act%=MOD;
	}
	return act;
}
void solve()
{
	int i;
	pos[1]=aranj(k,grd[1]);
	rez=pos[1];
	for (i=2; i<=n; i++)
	{
		pos[i]=B[grd[i]-1];
		rez*=pos[i];
		if (rez>=MOD)
			rez%=MOD;
	}
}
int main()
{
	freopen("colorare3.in","r",stdin);
	freopen("colorare3.out","w",stdout);
	read();
	precompute();
	solve();
	printf("%lld\n",rez);
	return 0;
}