#include<bits/stdc++.h>
using namespace std;
const int N=500;
const double eps=1e-8;
const double inf=1e12;
int T,n,t1,t2;
double C,ans,a[N+5],b[N+5],f[N+5][N+5];
struct pt{
    double x,v;
}w1[N+5],w2[N+5];
bool cmp(pt ax,pt bx){
    return ax.v<bx.v;
}
bool pd1(int i,int j,double t){
    if(!i) return 1;
    return w1[i].x+w1[i].v*t>w1[j].x+w1[j].v*t+eps;
}
bool pd2(int i,int j,double t){
    if(!i) return 1;
    return w2[i].x+w2[i].v*t>w2[j].x+w2[j].v*t+eps;
}
int main()
{
    // freopen("tiii.in","r",stdin);
    // freopen("tiii.out","w",stdout);
    scanf("%d",&T);
    while(T--){
        scanf("%lf%d",&C,&n);
        t1=t2=0;
        for(int i=1;i<=n;i++){
            scanf("%lf",&a[i]);
        }
        for(int i=1;i<=n;i++){
            scanf("%lf",&b[i]);
            if(a[i]<0) w1[++t1]=(pt){-a[i],b[i]};
            else w2[++t2]=(pt){a[i],b[i]};
        }
        sort(w1+1,w1+t1+1,cmp);
        sort(w2+1,w2+t2+1,cmp);
        for(int i=0;i<=t1;i++){
            for(int j=0;j<=t2;j++) f[i][j]=inf;
        }
        ans=inf;
        f[t1][t2]=0;
        for(int i=t1;i>=0;i--){
            for(int j=t2;j>=0;j--){
                double nd=(w1[i].x+w1[i].v*f[i][j])/(C-w1[i].v);
                for(int p=i-1;p>=0;p--){
                    if(pd1(p,i,f[i][j])){
                        f[p][j]=min(f[p][j],f[i][j]+2*nd);
                    }
                    if(p) nd=max(nd,(w1[p].x+w1[p].v*f[i][j])/(C-w1[p].v));
                }
                if(!j) f[0][0]=min(f[0][0],f[i][j]+nd);
                nd=(w2[j].x+w2[j].v*f[i][j])/(C-w2[j].v);
                for(int p=j-1;p>=0;p--){
                    if(pd2(p,j,f[i][j])){
                        f[i][p]=min(f[i][p],f[i][j]+2*nd);
                    }
                    if(p) nd=max(nd,(w2[p].x+w2[p].v*f[i][j])/(C-w2[p].v));
                }
                if(!i) f[0][0]=min(f[0][0],f[i][j]+nd);
            }
        }
        printf("%.8f\n",f[0][0]);
    }
    return 0;
}