Sentence 1: Pete had been looking forward to building a treehouse for years. 
 Sentence 3: Pete gathered all the wood and materials, and was excited to start 
 Sentence 4:  But 10 minutes into building, Seth wandered off to play video games 
 Sentence 5:  He realized his son didn't care about the project as much as he did 
 Given Sentence 2: When his son Seth turned 8, he decided they could build one together.