#include<bits/stdc++.h>

 using namespace std;

 #define pb(x) push_back(x)

 #define ll long long

 #define mk(x, y) make_pair(x, y)

 #define lson l, m, rt<<1

 #define mem(a) memset(a, 0, sizeof(a))

 #define rson m+1, r, rt<<1|1

 #define mem1(a) memset(a, -1, sizeof(a))

 #define mem2(a) memset(a, 0x3f, sizeof(a))

 #define rep(i, a, n) for(int i = a; i<n; i++)

 #define ull unsigned long long

 typedef pair<int, int> pll;

 const double PI = acos(-1.0);

 const double eps = 1e-;

 const int mod = 1e9+;

 const int inf = 1e4;

 const int dir[][] = { {-, }, {, }, {, -}, {, } };

 const int maxn = 2e5+;

 int num, q[maxn*], head[maxn*], dis[maxn*], s, t;

 struct node

 {

     int to, nextt, c;

     node(){}

     node(int to, int nextt, int c):to(to), nextt(nextt), c(c){}

 }e[maxn*];

 int bfs() {

     mem(dis);

     int st = , ed = ;

     dis[s] = ;

     q[ed++] = s;

     while(st<ed) {

         int u = q[st++];

         for(int i = head[u]; ~i; i = e[i].nextt) {

             int v = e[i].to;

             if(!dis[v]&&e[i].c) {

                 dis[v] = dis[u]+;

                 if(v == t)

                     return ;

                 q[ed++] = v;

             }

         }

     }

     return ;

 }

 int dfs(int u, int limit) {

     int cost = ;

     if(u == t)

         return limit;

     for(int i = head[u]; ~i; i = e[i].nextt) {

         int v = e[i].to;

         if(e[i].c&&dis[v] == dis[u]+) {

             int tmp = dfs(v, min(e[i].c, limit-cost));

             if(tmp>) {

                 e[i].c -= tmp;

                 e[i^].c += tmp;

                 cost += tmp;

                 if(cost == limit)

                     break;

             } else {

                 dis[v] = -;

             }

         }

     }

     return cost;

 }

 int dinic() {

     int ans = ;

     while(bfs()) {

         ans += dfs(s, inf);

     }

     return ans;

 }

 void add(int u, int v, int c) {

     e[num] = node(v, head[u], c); head[u] = num++;

     e[num] = node(u, head[v], c); head[v] = num++;

 }

 void init() {

     mem1(head);

     num = ;

 }

 int main()

 {

     int T, m, n, x, y, q, p, z;

     cin>>T;

     while(T--) {

         init();

         int sum = ;

         scanf("%d%d%d%d", &n, &m, &p, &q);

         s = p, t = q;

         while(m--) {

             scanf("%d%d%d", &x, &y, &z);

             add(x, y, z);

             sum += z;

         }

         int ans = dinic();

         if(ans == ) {

             cout<<"Inf"<<endl;

             continue;

         }

         sum -= ans;

         for(int i = ; i<num; i+=) {

             if(e[i].c == ) {

                 e[i].c = ;

                 e[i^].c = inf;

             } else if(e[i^].c==) {

                 e[i].c = inf;

                 e[i^].c = ;

             } else {

                 e[i].c = e[i^].c = inf;

             }

         }

         ans = dinic();

         printf("%.2f\n", 1.0*sum/ans);

     }

 }