Final answer:
The midnight deadline for Helen's deposit at First Bank, given that the bank is closed on weekends, would likely be Monday, 11:59 PM. However, bank policies may vary.
Step-by-step explanation:
The 'midnight deadline' in banking terms usually refers to the time by which all the transactions of the day must be posted or processed. In the case of Helen's deposit, if the bank is closed on weekends, then the transactions would not be processed until the next business day, which would be Monday. Therefore, the midnight deadline for First Bank, in this case, would likely be Monday, 11:59 PM. However, bank policies can differ, and some banks use the end of the day on which the deposit is made as the cutoff, which would be Friday. If in doubt, it's best to check with the individual bank's policy on transaction processing.