Is the passage of dialogue written correctly or incorrectly?

Then he added, "I have a new idea for a tree house." "Will it cost a lot?" his mother asked. "I think we can do it for free," Vernon replied.

A.
incorrectly

B.
correctly

Question

Is the passage of dialogue written correctly or incorrectly? 

    Then he added, "I have a new idea for a tree house." "Will it cost a lot?" his mother asked. "I think we can do it for free," Vernon replied.
 
 A.
incorrectly
 
 B.
correctly

anonymous · Answer

Punctuation seems to be all in the right spot, but the lay-out is all wrong, it should be like this;
Then he added, "I have a new idea for a tree house."
"Will it cost a lot?" his mother asked.
"I think we can do it for free." Vernon replied.
So I would have to say A, incorrect.

anonymous · Answer

Okay, Thank you