My rational for choosing this section of the film is this is the point that drives the plot onwards, it gives it reason.
The extract relates to the film as a whole because it is what the main plot is about why the private detective and marian crane sister and boyfriend go to the bates motell. It is why Marian crane dose not go back home and give the money back which she was planning on doing.
The film is constructed to the story being told as  it follows a linear path, with this as a major road mark on the path
The fil uses other ways then narrative sequence for example after Crane goes into her room Bates is left in his den, but then he moves a picture to reveal a peep hole the looks into cranes room revealing that this is somthing that bates has done before and Crane is not the first of his prying eyes. The peep whole also ads confusion after Crane is killed you think Bates did it as he was looking into Cranes room, but then you hear bates yelling at his mother for killing Crane. It ads confusion because the idea that bates had killed crane was planted in the audiances mind from the peep hole. Another way this develops the narrative was that Crane decided to return the money she stole she took a shower. The shower was her becoming clean and moraly right again washing off the sins of what she did, which is why the audiance feels bad for sarrow for her even though she had done somthing wrong. It makes her character good again.
The engagment between our characters is that Bates dressed up as his mother to kill Crane. Before bates kills Crane he only see's her through the peep whole before she is about to take a shower. When ever bates feels atraction for a girl part of his brain takes over to make himself think that he is the mother that he killed, he belives that since he was jealouse of his mother and her lovers when ever he is attracted to a girl the mother gets jealouse. Thats why Bates couldnt get close to Crane after he became attracted to her, the wall that he looks through symbolizes the mother side of his brain after he bacame attracted to her the mother side blocked him from getting close to Crane, only when he dressed up as the mother was he able to aproach her.