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: The Design is Final.. Sentence 1: Scientists have been working at Los Alamos on a new bomb. Sentence 2: The theory was easy to develop. Sentence 3: Now they wait on the material for their gadget to be produced. Sentence 4: They determined what material would be needed. Sentence 5: They decided on a final design.
A:
53