#include <bits/stdc++.h>
using namespace std;
#define DePrint(A...) { fprintf(stderr, A); }
typedef long long LL;
const int kMaxN = 2000 + 10;
const int kMaxV = 300 + 10;
const LL kInf = 100000000;
LL floyd[kMaxV][kMaxV];
int n, m, v_cnt, e_cnt;
int room[kMaxN][2];
double p[kMaxN], q[kMaxN], dp[kMaxN][kMaxN][2];
inline LL Dis(int i, int a, int b) {
  return floyd[room[i - 1][a]][room[i][b]];
}
int main() {
  scanf("%d %d %d %d", &n, &m, &v_cnt, &e_cnt);
  for (int i = 1; i <= n; i++)
    scanf("%d", &room[i][0]);
  for (int i = 1; i <= n; i++)
    scanf("%d", &room[i][1]);
  for (int i = 1; i <= n; i++)
    scanf("%lf", &p[i]);
  for (int i = 1; i <= n; i++)
    q[i] = 1 - p[i];
  memset(floyd, 0x3F, sizeof(floyd));
  for (int i = 1; i <= e_cnt; i++) {
    int u, v, w;
    scanf("%d %d %d", &u, &v, &w);
    floyd[u][v] = floyd[v][u] = min(floyd[u][v], (LL) w);
  }
  for (int i = 1; i <= v_cnt; i++)
    floyd[i][i] = 0;
  for (int k = 1; k <= v_cnt; k++)
    for (int i = 1; i <= v_cnt; i++)
      for (int j = 1; j <= v_cnt; j++)
        floyd[i][j] = min(floyd[i][j], floyd[i][k] + floyd[k][j]);
  for (int i = 1; i <= n; i++)
    for (int j = 0; j <= m; j++)
      dp[i][j][0] = dp[i][j][1] = kInf;
  dp[1][0][0] = dp[1][1][1] = 0;
  for (int i = 2; i <= n; i++) {
    dp[i][0][0] = dp[i - 1][0][0] + Dis(i, 0, 0);
    for (int j = 1; j <= min(i, m); j++) {
      dp[i][j][0] = min(dp[i - 1][j][0] + Dis(i, 0, 0),
                        dp[i - 1][j][1] + Dis(i, 0, 0) * q[i - 1]
                                        + Dis(i, 1, 0) * p[i - 1]);
      dp[i][j][1] = min(dp[i - 1][j - 1][0] + Dis(i, 0, 0) * q[i]
                                            + Dis(i, 0, 1) * p[i],
                        dp[i - 1][j - 1][1] + Dis(i, 0, 0) * q[i - 1] * q[i]
                                            + Dis(i, 0, 1) * q[i - 1] * p[i]
                                            + Dis(i, 1, 0) * p[i - 1] * q[i]
                                            + Dis(i, 1, 1) * p[i - 1] * p[i]);
    }
  }
  double ans = kInf;
  for (int i = 0; i <= m; i++) {
    ans = min(ans, dp[n][i][0]);
    ans = min(ans, dp[n][i][1]);
  }
  printf("%.2lf\n", ans);
  return 0;
}