Once upon a time, an old woman had two large water pots. Each hung on the end of a pole which she carried across her neck. One of the pots had a crack in it while the other pot was perfect, From the river to the house, the cracked pot arrived only half full. And the other pot was always full. The perfect pot took pride in its talent.  But the poor cracked pot felt sad for its own disadvantage. One day by the river the cracked pot said to the woman, "I feel bad about myself, because the crack in me causes water to come out all the way back to your house." The old woman smiled and said, "Why are there flowers on your side of the road, but not on the other pot's side? That's because I have always known about your crack. So I planted flowers on your side of the road, and every day while we walk back, you water them. For two years I have been able to pick these beautiful flowers to decorate my house, There would not be this beauty without you. Each of us has our own cracks. But the cracks make our lives so interesting and beautiful." So, to all the cracked pot friends, have a great day and remember to smell the flowers on your side of the road! If each of the two pots could be filled with 20 kilos of water, the woman would probably get   _   kilos of water from the river to the house.
10 20 30 40