#include<bits/stdc++.h>
#define Clr(x) memset(x,0,sizeof(x))
#define x1 Starrykiller
#define x2 Arcaea
#define y1 Minecraft
#define y2 Milmon
#define N 100005
using namespace std;
int n,s,w[N],a[N],sum[N],up[N];
int st[N],ed[N],C,ans;
int id(int x,int y){
	if(x<1 || y<1)return 0;
	return n*(y-1)+x;
}
int getsum(int x1,int x2,int y1,int y2){
	--x1; --y1; return sum[id(x2,y2)]-sum[id(x1,y2)]-sum[id(x2,y1)]+sum[id(x1,y1)];
}
void calc(int L,int R){
	for(int i=1;i<=s;++i){
		for(int j=st[i],r=0;j<=ed[i];++j){
			if(getsum(L,R,j,j)==0)++r;
			else r=0; ans=max(ans,(R-L+1)*r);
		}
	} int lmax[2][2],rmax[2][2],mid=0;
	Clr(lmax); Clr(rmax);
	for(int i=1;i<=s;++i){
		int mxl=0,mxr=0;
		for(int j=st[i];j<=ed[i];++j){
			if(getsum(L,R,j,j))break;
			++mxl;
		}
		for(int j=ed[i];j>=st[i];--j){
			if(getsum(L,R,j,j))break;
			++mxr;
		}
		if(mxl==w[i])mid+=w[i];
		else{
			if(mxl>lmax[0][0])lmax[0][0]=mxl,lmax[0][1]=i;
			else if(mxl>lmax[1][0])lmax[1][0]=mxl,lmax[1][1]=i;
			if(mxr>rmax[0][0])rmax[0][0]=mxr,rmax[0][1]=i;
			else if(mxr>rmax[1][0])rmax[1][0]=mxr,rmax[1][1]=i;
		}
	}
	for(int p=0;p<2;++p){
		for(int q=0;q<2;++q){
			if(lmax[p][1]!=rmax[q][1])
				ans=max(ans,(R-L+1)*(mid+lmax[p][0]+rmax[q][0]));
		}
	} ans=max(ans,(R-L+1)*(mid+lmax[0][0]));
	ans=max(ans,(R-L+1)*(mid+rmax[0][0]));
}
void Solve(){
	//Clear
	C=ans=0; Clr(sum); Clr(up); 
	Clr(ed); Clr(w); Clr(a); Clr(st);
	
	//input and prework
	cin>>s>>n;
	for(int i=1;i<=s;++i){
		cin>>w[i]; st[i]=C+1;
		for(int j=1;j<=n;++j){
			for(int k=1;k<=w[i];++k){
				char ch; cin>>ch;
				a[id(j,C+k)]=ch-'0';
			}
		} C+=w[i]; ed[i]=C;
	} int m=sqrt(C*n);
	for(int i=1;i<=s;++i){
		for(int j=1;j<=n;++j){
			for(int k=st[i];k<=ed[i];++k)
				sum[id(j,k)]=a[id(j,k)]+sum[id(j-1,k)]+sum[id(j,k-1)]-sum[id(j-1,k-1)];
		}
	}
	for(int j=1;j<=C;++j){
		for(int i=1,lst=0;i<=n+1;++i){
			if(i>n || a[id(i,j)]){
				for(int k=lst+1;k<=i-1;++k)up[id(k,j)]=i-1;
				lst=i;
			}
		}
	}
	
	//solver
	if(n<=m){
		for(int L=1;L<=n;++L){
			for(int R=L;R<=n;++R)
				calc(L,R);
		}
	} else {
		for(int i=1;i<=n;++i){
			for(int j=1;j<=C;++j)
				calc(i,up[id(i,j)]);
		}
	} cout<<ans<<'\n';
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr); cout.tie(nullptr);
	int Ks; cin>>Ks; while(Ks--)Solve();
	return 0;
}