I received an online assessment after applying. The questions are not typical LeetCode-style problems. Instead, each question has multiple levels that build on the previous level.

The CodeSignal assessment for Ramp typically consists of 4 questions that build on each other and must be answered in order.

Could you please implement a Python program that simulates basic bank account operations? The program should include the following features:

• A function to create a new customer account if it doesn't already exist.
• A function to deposit money into an existing account and return the total balance. If the account doesn't exist, the function should return None.
• A function to process payments by deducting the amount from the customer's balance, but only if sufficient funds are available. If the balance is insufficient, the function should return a message indicating so. If the account doesn't exist, it should return None.

Each account should be identified by the customer's name, and the program should handle multiple customers.