text: function mutateMyStrings (s1, s2) {
  
    let arr1 = s1.split('');
    let arr2 = s2.split('');
    let returnString = (s1 + '\n');
  
    for (var i in arr1) {
      if (arr1[i] !== arr2[i]){
        arr1[i] = arr2[i];
        returnString = returnString.concat(arr1.join('') + '\n');
      }
    }
    return returnString;
  }