John had a drinking problem in school. After he graduated, John's friend Darren used his connections to help him get a job at a bank. Darren thought that working at the/a bank would make John more responsible and help him quit drinking completely. Darren's friend Peter, who worked there as a manager, accepted John as a full-time employee.
Is either option acceptable in this case, or should the definite article "the" be used because the word "bank" has already been mentioned with the indefinite article "a"? If either can be used, what is the nuance? Thank you.