Sentence 1: Rick wanted shiny white teeth! 
 Sentence 3: Then his aunt suggested he try brushing with baking soda 
 Sentence 4:  Rick was skeptical, but he began following her advice anyways 
 Sentence 5:  And in under a month, his teeth had become noticeably whiter! 
 Given Sentence 2: He hates how dull his teeth always looked.