#include<bits/stdc++.h>
using namespace std;
const int N=2005;
const double maxi=800050000;
int n,m,v,e;
int c[N][2];
double k[N];
double d[N][N];
double f[N][N][2];
int read(){
	int sum=0,f=1;
	char ch=getchar();
	while(ch>'9'||ch<'0')
	{
		if(ch=='-')f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9')
	{
		sum=(sum<<3)+(sum<<1)+ch-'0';
		ch=getchar();
	}
	return sum*f;
}
int main(){
//	freopen("classroom.in","r",stdin);
//	freopen("classroom.out","w",stdout);
	n=read();
	m=read();
    v=read();
    e=read();
    for(int i=1;i<=n;i++)
    c[i][0]=read();
    for(int i=1;i<=n;i++)
	c[i][1]=read(); 
	for(int i=1;i<=n;i++)
	scanf("%lf",&k[i]);

	for(int i=1;i<=v;i++)
	for(int j=1;j<i;j++)
	d[i][j]=d[j][i]=maxi;	
	int x,y;
	double w;
	for(int i=1;i<=e;i++)
	{
	    x=read();
	    y=read();
	    scanf("%lf",&w);
	    if(w<d[x][y])d[x][y]=d[y][x]=w;
	}
	for(int t=1;t<=v;t++) 
	for(int i=1;i<=v;i++)
	for(int j=1;j<i;j++)
	if(d[i][j]>d[i][t]+d[t][j])
   	d[i][j]=d[j][i]=d[i][t]+d[t][j];
   	
	for(int i=1;i<=n;i++)
	for(int j=0;j<=m;j++)
	f[i][j][0]=f[i][j][1]=maxi;
	f[1][0][0]=0;
	f[1][1][1]=0;
    for(int i=2;i<=n;i++)
    for(int j=0;j<=m;j++)
	{
		f[i][j][0]=min(f[i][j][0],f[i-1][j][1]+k[i-1]*d[c[i-1][1]][c[i][0]]+(1-k[i-1])*d[c[i-1][0]][c[i][0]]);
		f[i][j][0]=min(f[i][j][0],f[i-1][j][0]+d[c[i-1][0]][c[i][0]]);
		if(j!=0){
		f[i][j][1]=min(f[i][j][1],f[i-1][j-1][0]+k[i]*d[c[i-1][0]][c[i][1]]+(1-k[i])*d[c[i-1][0]][c[i][0]]);
		f[i][j][1]=min(f[i][j][1],f[i-1][j-1][1]+k[i]*k[i-1]*d[c[i-1][1]][c[i][1]]+k[i]*(1-k[i-1])*d[c[i-1][0]][c[i][1]]+(1-k[i])*k[i-1]*d[c[i-1][1]][c[i][0]]+(1-k[i])*(1-k[i-1])*d[c[i-1][0]][c[i][0]]);
	   }
}
	double ans=maxi;
    for(int j=0;j<=m;j++)
    for(int t=0;t<2;t++)
    {
	ans=min(ans,f[n][j][t]);
	}
    printf("%.2lf",ans);
	return 0;
}

/**************************************************************
	Problem: 2349
	User: admin
	Language: C++
	Result: Accepted
	Time:955 ms
	Memory:96328 kb
****************************************************************/