#include <bits/stdc++.h>

using namespace std;

#define int long long

int map_max(map<char, int> mp) {
    int max_val=0;
    for(auto elem:mp) max_val=max(max_val, elem.second);
    return max_val;
}

int32_t main() {
    int t;
    cin >> t;
    for(int q=0; q<t; ++q) {
        int ra, length;
        cin >> ra >> length;
        string arr[ra];
        for(int i=0; i<ra; ++i) cin >> arr[i];
        int max_score=0, score=0;
        vector<pair<map<char,int>, map<char,int>>> values(length);
        //ilk kesite göre harfleri al
        for(int j=0; j<length; ++j)
        for(auto str : arr) {
            //Her stringin o indexi için vectorun o index kısmındaki o array harfini 1 artır.
            values[j].second[str[j]]++;
        }
        //Kesit=0 için max değeri bul
        for(auto elem : values) score+=map_max(elem.first);
        for(auto elem : values) score+=map_max(elem.second);
        max_score=max(max_score, score);
        //Kesitler
        for(int i=1; i<ra; ++i) {
            score=0;
            //(i-1)ci stringin her karakteri için vec[i].first[char] artır vec[i].second[char] azalt.
            for(int j=0; j<length; ++j) {values[j].first[arr[i-1][j]]++; values[j].second[arr[i-1][j]]--;}
            //Yeni skoru bul
            for(auto elem : values) score+=map_max(elem.first);
            for(auto elem : values) score+=map_max(elem.second);
            max_score=max(max_score, score);
        }
        cout << max_score << endl;
    }
    return 0;
}