C++ :

#pragma GCC optimize ("O2")
#include <bits/stdc++.h>
#define inf 0x3f3f3f3f
#define met(a,b) memset(a,b,sizeof a)
#define pb push_back
#define mp make_pair
#define rep(i,l,r) for(int i=(l);i<=(r);++i)
#define inf 0x3f3f3f3f
using namespace std;
typedef long long ll;
const int N = 1e3+50;;
const int M = 6e5;
const int mod = 19260817;
const int mo=123;
const double pi= acos(-1.0);
typedef pair<int,int>pii;
int n,m,S,T;
ll dis[N],dp[2][N];
int vis[N],mark[N];
vector<pii>edg[N];
ll spfa(int s,int t,ll x){
    for(int i=0;i<N;i++)dis[i]=1e18,vis[i]=0;
    queue<int>q;
    vis[s]=1;
    dis[s]=0;
    q.push(s);
    while(!q.empty()){
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(int i=0;i<edg[u].size();i++){
            int v=edg[u][i].first;
            int w=edg[u][i].second;
            if(!mark[v])continue;
            if(dis[v]>dis[u]+x+w){
                dis[v]=dis[u]+x+w;
                if(!vis[v]){
                    q.push(v);
                    vis[v]=1;
                }
            }
        }
    }

    return dis[t];
}
void spfa2(int s,ll x){
    int ty=(s==S);
    for(int i=0;i<N;i++)dp[ty][i]=1e18,vis[i]=0;
    queue<int>q;
    vis[s]=1;
    dp[ty][s]=0;
    q.push(s);
    while(!q.empty()){
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(int i=0;i<edg[u].size();i++){
            int v=edg[u][i].first;
            int w=edg[u][i].second;
            if(dp[ty][v]>dp[ty][u]+x+w){
                dp[ty][v]=dp[ty][u]+x+w;
                if(!vis[v]){
                    q.push(v);
                    vis[v]=1;
                }
            }
        }
    }
}
bool check(ll x){
    //x=3;
    ll len1=spfa(S,T,x);
    spfa2(S,x);
    spfa2(T,x);
    ll len2=1e18;
    for(int i=1;i<=n;i++){
        if(mark[i])continue;
        //printf("%lld %lld\n",dp[1][i],dp[0][i]);
        len2=min(len2,dp[1][i]+dp[0][i]);
    }
    //printf("len1:%lld len2:%lld\n",len1,len2);
   // system("pause");
    if(len1>len2)return false;
    return true;
}
int main(){
    int TT;
    scanf("%d",&TT);
    while(TT--){
        met(mark,0);
        for(int i=0;i<N;i++)edg[i].clear();
        scanf("%d%d%d%d",&n,&m,&S,&T);
        while(m--){
            int u,v,w;
            scanf("%d%d%d",&u,&v,&w);
            edg[u].pb(mp(v,w));
            edg[v].pb(mp(u,w));
        }
        int k;
        scanf("%d",&k);
        while(k--){
            int u;
            scanf("%d",&u);
            mark[u]=1;
        }
        ll l=0,r=1e15,ans=-1;
        while(l<=r){
            ll mid=(l+r)/2;
           //printf("mid:%lld\n",mid);
            if(check(mid))l=mid+1,ans=mid;
            else r=mid-1;
        }
        if(ans==-1)puts("Impossible");
        else if(ans==1e15)puts("Infinity");
        else {
            ll res=ans;
            for(int i=1;i<=5;i++){
                if(check(res+i))ans=res+i;
            }
            printf("%lld\n",ans);
        }
    }
    return 0;
}