Given the following context:  The story focuses on four 19-year-old friends: Joanne, Cassandra, Shannon and Kerrys. They all meet one other at a diner, where they see Dillon and Smoothy. Unbeknownst to Dillon, Shannon has a crush on him. As the police turn up, Dillon and Smoothy run off and Dillon accidentally drops a stolen diamond into Cassandra's bag. The four girls then walk out and go their separate ways home. First, the story focuses on Shannon: she walks into her home just as her mother is leaving her father. She loses her temper and runs away, going to Jo's home, who has to rush to work, telling her she does not have time to talk. Jo calls Shannon over to the supermarket where she works, but tells her to leave as soon as she arrives. When she refuses, Dillon kisses Jo, upsetting Shannon, whom he asked out earlier in the day, so she grabs a Pringles tube from the shop and runs away. After getting drunk at a bar, she goes to a tunnel where she sprays graffiti on the wall, is attacked by a gang and then taken in by Kelly, who saved her. Shannon realizes that Kelly seems to be looking for the Pringles. This is later confirmed when she finds out that she is searching for "15 diamonds". One is already in Cassandra's bag and the rest are in the can that fell out of Shannon's bag in the tunnel. She escapes by knocking Kelly out with the bathroom door. She finds the diamonds by going back to where she was attacked, and leaves a message informing Jo about them. Later, Shannon tracks down her mother and accuses her of not caring about her, especially when she forced her to get an abortion. Her story ends with her holding the diamonds above a bridge, suggesting she is about to commit suicide. Jo, Cassandra and Kerrys appear to threaten Shannon into handing the diamonds over.  answer the following question:  Who works at the supermarket?
A:
Jo