In this task, you're given the title of a story consisting of five sentences, numbered 1 through 5. Your job is to determine which two sentences need to be swapped sentences in order to make a story that makes complete sense and is befittingly titled. Indicate your answer using the numbers of the two sentences in order, such as '34' or '25'. The first digit refers to the sentence which should come first in the story.
Q: Title: Chemistry test. Sentence 1: I was nervous, but the test seemed easy. Sentence 2: I studied for a week straight before the test. Sentence 3: I had a chemistry test last week. Sentence 4: When I got my test back, I saw that I got a good grade. Sentence 5: I was happy that my grade reflected my hard work.
A: 
13