#include <iostream>

 #include <cstdio>

 #include <cstring>

 #include <cmath>

 #include <queue>

 using namespace std;

 const int maxn=;

 const double eps=1e-;

 int map[maxn],flag[maxn];

 double p[maxn],A[maxn][maxn];

 int cnt,n,m,st,ed,d;

 int dcmp(double x)

 {

     if(fabs(x)<eps) return ;

     else if(x->eps) return ;

     return -;

 }

 void swap(double &a,double &b){double t=a;a=b;b=t;}

 bool bfs()

 {

     memset(flag,-,sizeof(flag));

     queue<int>Q;

     cnt=;flag[st]=cnt++;

     Q.push(st);

     bool ret=false;

     while(!Q.empty())

     {

         int u=Q.front();Q.pop();

         for(int i=;i<=m;i++)

         {

             int v=(u+i)%(*n-);

             if(dcmp(p[i])==) continue;

             if(flag[v]!=-) continue;

             flag[v]=cnt++;

             if(map[v]==ed) ret=true;

             Q.push(v);

         }

     }

     return ret;

 }

 void bulidmatrix()

 {

     memset(A,,sizeof(A));

     for(int i=;i<*n-;i++)

     {

         if(flag[i]==-) continue;

         int u=flag[i];A[u][u]=;

         if(map[i]==ed){A[u][cnt]=;continue;}

         for(int j=;j<=m;j++)

         {

             int v=(i+j)%(*n-);

             if(flag[v]==-) continue;

             v=flag[v];

             A[u][v]-=p[j];A[u][cnt]+=p[j]*j;

         }

     }

 }

 void gauss(int n)

 {

     int i,j,k,r;

     for(i=;i<n;i++)

     {

         r=i;

         for(j=i+;j<n;j++)

             if(fabs(A[j][i])>fabs(A[r][i])) r=j;

         if(dcmp(A[r][i])==) continue;

         if(r!=i) for(j=;j<=n;j++) swap(A[r][j],A[i][j]);

         for(k=;k<n;k++) if(k!=i)

             for(j=n;j>=i;j--) A[k][j]-=A[k][i]/A[i][i]*A[i][j];

     }

 }

 int main()

 {

     int i,j,t;

     scanf("%d",&t);

     while(t--)

     {

         scanf("%d%d%d%d%d",&n,&m,&ed,&st,&d);

         for(i=;i<=m;i++){ scanf("%lf",p+i);p[i]/=;}

         if(st==ed){ printf("0.00\n");continue;}

         for(i=;i<n;i++) map[i]=i;

         for(i=n,j=n-;i<*n-;i++,j--) map[i]=j;

         if(d==) st=*n--st;

         if(!bfs()){ printf("Impossible !\n");continue;}

         bulidmatrix();gauss(cnt);

         for(i=cnt-;i>=;i--)

         {

             for(j=i+;j<cnt;j++)

                 A[i][cnt]-=A[j][cnt]*A[i][j];

             A[i][cnt]/=A[i][i];

         }

         printf("%.2lf\n",A[][cnt]);

     }

     return ;

 }