What is time complexity of the code?

Question

 def multi_merge_v1(lst_of_lsts):
      all = [e for lst in lst_of_lsts for e in lst]
      merged = []
      while all != []:
            minimum = min(all)
            merged += [minimum]
            all.remove(minimum)
      return merged

What is the time complexity of this code? is it O(2mn)? Because creating "all" requires mn steps and also while requires mn steps

Answer 1

It is O((m*n)**2) because while loop is executed m*n times and min(all), all.remove(minimum) are O(n*m) operations.