#include <cstdio>
typedef long long ll;
const int M=int(1e9)+7;
ll pow(ll a,ll b){
if(b==0) return 1;
ll ret=pow(a,b/2);
ret=(ret*ret)%M;
if(b&1) ret=(ret*a)%M;
return ret;
}
int main()
{
int p,q,n,k;
scanf("%d%d%d%d",&p,&q,&n,&k);
if(q==0){
if(k==0) puts("0");
else puts("1");
return 0;
} else if(p==q){
if(k==n) puts("1");
else puts("0");
return 0;
}
ll bunja = (pow(p-q,n) - pow(q,k) * pow(p-q, n-k)%M + M)%M;
ll bunmo = (pow(p-q,n) - pow(q,n) + M)%M;
printf("%d\n",int( bunja*pow(bunmo,M-2)%M ));
return 0;
}
