Continue to write father and son

Father and his son stay at home. My son is singing.

"You have to stop." Father said. "Your father is going to read his book. Dad can't listen to songs while reading. "

"Why not?" The son asked.

"Because dad can only think of one thing at a time."

The son stopped singing. He sat quietly. Father lit a cigar and went on reading.

After a while, the son asked, "Dad, can you still consider only one thing at a time?"

"Yes, my son. You are right. "

"Then, you should stop reading and think about the slippers on your right foot." The son said.