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: Devon patrolled the neighborhood in his cop car that night. Sentence 2: When he saw an old lady being mugged, he stopped. Sentence 3: He run after the mugger to retrieve the purse he had stolen. Sentence 4: He gave back the purse to the old lady. Sentence 5: He brought the mugger to the police station to interrogate him. Choices: a. Freezing cold. b. Cop and mugger.
b