/*
Éèdp[i][j][0/1]±íʾǰi²½Ê¹ÓÃÁËj´ÎÉêÇëµÄ×îСÆÚÍû
״̬תÒÆ:
dp[i][j][0] = min(dp[i - 1][j][0] + w[c[i-1]][c[i]], dp[i - 1][j][1] + w[d[i-1]][c[i]] * (1 - p[i - 1]) + w[c[i-1]][c[i]] * p[i - 1]);
dp[i][j][1] = min(dp[i - 1][j - 1][0] + w[c[i - 1]][d[i]] * p[i] + w[c[i - 1]][c[i]] * (1 - p[i]),
dp[i - 1][j - 1][1] + w[c[i - 1]][d[i]] * (1 - p[i - 1]) * p[i] + w[d[i - 1]][d[i]] * p[i - 1] * p[i] + w[c[i - 1]][c[i]] * (1 - p[i - 1]) * (1 - p[i]) + w[d[i - 1]][c[i]] * p[i - 1] * (1 - p[i]);
´ð°¸:min(j=0->m) {dp[n][j][0], dp[n][j][1]}

ÆäÖÐwΪ×î¶Ì·
*/
#include <cstdio>
#include <algorithm>
#include <iostream>
#include <cstring>
#include <string>
#include <queue>
#include <deque>
#include <cmath>
#include <vector>
#include <map>
#include <unordered_map>
#include <stack>
#include <set>
#include <bitset>
#define LL long long
#define ULL unsigned long long
#define IT set<int>::iterator
using namespace std;
const int MAXN = 2005;
int n, m, v, e, c[MAXN], d[MAXN], f[MAXN][MAXN];
double k[MAXN], dp[MAXN][MAXN][2];
int read() {
    int x = 0, flag = 1;
    char c = getchar();

    while (c < '0' || c > '9') {
        if (c == '-')
            flag = 0;

        c = getchar();
    }

    while (c >= '0' && c <= '9') {
        x = x * 10 + c - '0';
        c = getchar();
    }

    return flag ? x : -x;
}
int main() {
    //  freopen("classroom2.in", "r", stdin);
    n = read(), m = read(), v = read(), e = read();

    for (int i = 1; i <= n; ++i)
        c[i] = read();

    for (int i = 1; i <= n; ++i)
        d[i] = read();

    for (int i = 1; i <= n; ++i)
        scanf("%lf", &k[i]);

    for (int i = 1; i <= v; ++i)
        for (int j = i + 1; j <= v; ++j)
            f[i][j] = f[j][i] = 1e9; //´íÒò:³õʼ»¯¹ý´óµ¼Ö±¬int

    for (int i = 1; i <= e; ++i) {
        int a = read(), b = read(), w = read();
        f[a][b] = f[b][a] = min(w, f[a][b]);
    }

    for (int k = 1; k <= v; ++k) { //floyd
        for (int i = 1; i <= v; ++i) {
            for (int j = i + 1; j <= v; ++j) {
                if (f[i][k] + f[k][j] < f[i][j])
                    f[i][j] = f[j][i] = f[i][k] + f[k][j];
            }
        }
    }

    for (int i = 1; i <= n; ++i) {
        for (int j = 0; j <= m; ++j) {
            dp[i][j][0] = dp[i][j][1] = 2e9;
        }
    }

    dp[1][0][0] = dp[1][1][1] = 0;

    for (int i = 2; i <= n; ++i) {
        for (int j = 0; j <= min(i, m); ++j) {
            dp[i][j][0] = min(dp[i - 1][j][0] + f[c[i - 1]][c[i]],
                              dp[i - 1][j][1] + f[d[i - 1]][c[i]] * k[i - 1] + f[c[i - 1]][c[i]] * (1.0 - k[i - 1]));

            //          printf("%d %d 0 = min(%d + %d, %d + %lf + %lf)\n", i, j, dp[i - 1][j][0], f[c[i - 1]][c[i]], dp[i - 1][j][1], f[d[i - 1]][c[i]] * k[i - 1], f[c[i - 1]][c[i]] * (1.0 - k[i - 1]));
            if (j != 0)
                dp[i][j][1] = min(dp[i - 1][j - 1][0] + f[c[i - 1]][d[i]] * k[i] + f[c[i - 1]][c[i]] * (1.0 - k[i]),
                                  dp[i - 1][j - 1][1] + f[c[i - 1]][d[i]] * (1.0 - k[i - 1]) * k[i] + f[d[i - 1]][d[i]] * k[i - 1] * k[i] +
                                  f[c[i - 1]][c[i]] * (1.0 - k[i - 1]) * (1.0 - k[i]) + f[d[i - 1]][c[i]] * k[i - 1] * (1.0 - k[i]));

            //          printf("%d %d:%lf %lf\n", i, j, dp[i][j][0], dp[i][j][1]);
        }
    }

    double ans = 2e9;

    for (int i = 0; i <= m; ++i)
        ans = min(ans, min(dp[n][i][0], dp[n][i][1]));

    printf("%.2lf\n", ans);
    return 0;
}