#pragma GCC optimize "O3"
#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;

#define FOR(i,b,e) for(int i=b; i<=e; i++)
#define FORD(i,b,e) for(int i=b; i>=e; i--)
#define SIZE(x) ((int)x.size())
#define pb push_back
#define st first
#define nd second
#define sp ' '
#define ent '\n'

const int mod=1e9+7;
const int N=1010;

int memo[N][N];

int binom(int n, int k){
	if(n<0 || k<0 || k>n) return 0;
	if(memo[n][k]!=-1) return memo[n][k];
	if(k==0 || k==n) return memo[n][k]=1;
	return memo[n][k]=(binom(n-1, k)+binom(n-1, k-1))%mod;
}

void solve(){
	memset(memo, -1, sizeof(memo));
	ll ans=0;
	int a, b, k, c;
	cin>>a>>b>>k>>c;	
	if(a==c && b==c){
		cout<<k<<ent;
		return;
	}
	if(a!=c && b!=c){
		cout<<0<<ent;
		return;
	}
	FOR(i, 0, k) ans=(ans+(ll)i*binom(k, i))%mod;
	cout<<ans<<ent;
}

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	solve();
	return 0;
}