#pragma optimize("Bismillahirrahmanirrahim")
#pragma GCC optimize("O3,Ofast")
#pragma target("avx2")
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//Allahuekber
//ahmet23 orz...
//Sani buyuk Osman Pasa Plevneden cikmam diyor.
//FatihSultanMehmedHan
//YavuzSultanSelimHan
//AbdulhamidHan
#define author tolbi
#include <bits/stdc++.h>
using namespace std;
template<typename X, typename Y> istream& operator>>(istream& in, pair<X,Y> &pr) {return in>>pr.first>>pr.second;}
template<typename X, typename Y> ostream& operator<<(ostream& os, pair<X,Y> pr) {return os<<pr.first<<" "<<pr.second;}
template<typename X, typename Y> pair<X,Y> operator+(pair<X,Y> a, pair<X,Y> b) {pair<X,Y> c; c.first=a.first+b.first,c.second=a.second+b.second;return c;}
template<typename X, typename Y> pair<X,Y> operator-(pair<X,Y> a, pair<X,Y> b) {pair<X,Y> c; c.first=a.first-b.first,c.second=a.second-b.second;return c;}
template<typename X, typename Y> void operator+=(pair<X,Y> &a, pair<X,Y> b){a.first+=b.first,a.second+=b.second;}
template<typename X, typename Y> void operator-=(pair<X,Y> &a, pair<X,Y> b){a.first-=b.first,a.second-=b.second;}
template<typename X> istream& operator>>(istream& in, vector<X> &arr) {for(auto &it : arr) in>>it; return in;}
template<typename X> ostream& operator<<(ostream& os, vector<X> arr) {for(auto &it : arr) os<<it<<" "; return os;}
template<typename X, size_t Y> istream& operator>>(istream& in, array<X,Y> &arr) {for(auto &it : arr) in>>it; return in;}
template<typename X, size_t Y> ostream& operator<<(ostream& os, array<X,Y> arr) {for(auto &it : arr) os<<it<<" "; return os;}
#define int long long
#define endl '\n'
#define vint(x) vector<int> x
#define deci(x) int x;cin>>x;
#define decstr(x) string x;cin>>x;
#define cinarr(x) for (auto &it : x) cin>>it;
#define coutarr(x) for (auto &it : x) cout<<it<<" ";cout<<endl;
#define sortarr(x) sort(x.begin(),x.end())
#define sortrarr(x) sort(x.rbegin(),x.rend())
#define det(x) cout<<"NO\0YES"+x*3<<endl;
#define INF LONG_LONG_MAX
#define rev(x) reverse(x.begin(),x.end());
#define ios ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define tol(bi) (1LL<<((int)(bi)))
const int MOD = 1e9+7;
mt19937 ayahya(chrono::high_resolution_clock().now().time_since_epoch().count());
#include "cyberland.h"
#define ld long double
long double SIN = 1e15;
double solve(int32_t N, int32_t M, int32_t K, int32_t H, vector<int32_t> x, vector<int32_t> y, vector<int32_t> c, vector<int32_t> barr) {
K=min(K,23*3);
vector<vector<pair<int,int>>> arr(N);
for (int i = 0; i < M; i++){
arr[x[i]].push_back({y[i],c[i]});
arr[y[i]].push_back({x[i],c[i]});
}
priority_queue<pair<ld,int>,vector<pair<ld,int>>,greater<pair<ld,int>>> pq;
vector<ld> dp(N,SIN);
vector<ld> ldp(N,SIN);
vector<bool> pat(N,false);
auto dfs = [&](int node, auto dfs)->void{
pat[node]=true;
if (node==H) return;
for (int i = 0; i < arr[node].size(); i++){
if (pat[arr[node][i].first]) continue;
dfs(arr[node][i].first,dfs);
}
};
dfs(0,dfs);
pq.push({0,0});
for (int i = 0; i < N; i++){
if (barr[i]==0 && pat[i]){
pq.push({0,i});
}
}
auto bfs = [&](int ahmet23 = 23)->void{
fill(dp.begin(), dp.end(), SIN);
while (pq.size()){
int node = pq.top().second;
ld w = pq.top().first;
pq.pop();
if (dp[node]<=w) continue;
dp[node]=w;
if (node==H) continue;
for (int i = 0; i < arr[node].size(); i++){
if (dp[arr[node][i].first]<=w+arr[node][i].second) continue;
pq.push({w+arr[node][i].second,arr[node][i].first});
}
}
for (int i = 0; i < N; i++){
if (i==H) continue;
for (int j = 0; j < arr[i].size(); j++){
if (barr[arr[i][j].first]!=2) continue;
ldp[arr[i][j].first]=min(ldp[arr[i][j].first],dp[i]+arr[i][j].second);
}
}
};
for (int kal = K; kal >= 0; kal--){
bfs();
for (int i = 0; i < N; i++){
if (kal && barr[i]==2){
if (dp[i]==SIN) continue;
if (ldp[i]==SIN) continue;
dp[i]=min(dp[i],ldp[i]/2.0);
ldp[i]=SIN;
}
pq.push({dp[i],i});
}
}
bfs();
if (dp[H]==SIN) return -1;
return dp[H];
}
#ifdef tolbi
int32_t main() {
int32_t T;
assert(1 == scanf("%d", &T));
while (T--){
int32_t N,M,K,H;
assert(4 == scanf("%d %d %d\n%d", &N, &M, &K, &H));
vector<int32_t> x(M);
vector<int32_t> y(M);
vector<int32_t> c(M);
vector<int32_t> arr(N);
for (int32_t i=0;i<N;i++)
assert(1 == scanf("%d", &arr[i]));
for (int32_t i=0;i<M;i++)
assert(3 == scanf("%d %d %d", &x[i], &y[i], &c[i]));
printf("%.12lf\n", solve(N, M, K, H, x, y, c, arr));
}
}
#endif
