Given the task definition and input, reply with output. In this task, you're given five sentences, numbered 1 through 5, and two options a and b for possible titles for the story. Your job is to choose the title that better fits the story. Indicate your choice by 'a' or 'b'.

Sentence 1: Jimmy Jackson was a prison guard. Sentence 2: One day he was asked to watch over a high security offender. Sentence 3: He spent most of the day monitoring him closely. Sentence 4: Until the prisoner escaped as he was eating lunch. Sentence 5: The prisoner was hungry too, so he got a burger and was recaptured. Choices: a. Escape. b. Rare Book.
a