What is the differences and similarities of these two stories (The donkey and the mule) and (The peddler's mule) The Donkey and the Mule:
A Peddler set off on his usual journey. All of the things he would sell along the
way were packed on his donkey and his mule. The donkey walked along
easily until they started up the steep mountain path. The poor little donkey’s
load was more than he could bear. He begged the mule to take a little bit of
his load so that he could carry the rest more easily. But the Mule paid no
attention. At last, they reached the top of the mountain where there was a
small inn. The donkey was so exhausted that he fell to the ground. The next
morning the donkey still could not get to his feet. Not knowing what else to do, the Peddler added the donkey’s load to the mule’s load and went on without the donkey. The mule’s load was heavy, but his heart was even heavier. “If only I had helped the donkey just a little, I would not have a double load myself,” he reflected.

The Peddler’s Mule:
A Peddler took his mule to the seacoast to buy salt. On the way home, they
crossed a shallow stream where the mule accidentally slipped and fell. All of
the salt in the bags dissolved, and the mule’s load was much lighter. The
Peddler went back and bought even more salt than before. When they came
to the stream, the mule fell down on purpose. When he got up, his load was
again much lighter than before. The Peddler saw through the mule’s trick and
went back to the seacoast a third time. This time, instead of salt, he bought a
cargo of sponges. Again, the mule fell down when they reached the stream.
The sponges filled with water, and greatly increased his load. This time he
had only tricked himself.