In this task, you're given the title of a five-sentence story and the first four sentences. Your job is to write the last sentence of the story such that it seamlessly connects with the rest of the story.

Title: Guinea Pigs. Sentence 1: My niece bought as guinea pig for her ten year old daughter. Sentence 2: She bought another one for company. Sentence 3: She thought they were both females. Sentence 4: She was mistaken, and a litter was born.
She was able to sell the babies to a pet store.