Ln a bank the account numbers are all 8 digit numbers, and they all start with the digit 2. So, an account number can be represented as $2x_1x_2x_3x_4x_5x_6x_7$. An account number is considered to be a ‘magic’ number if $x_{1}x_{2}x_{3}$ is exactly the same as $x_{4}x_{5}x_{6}$ or $x_{5}x_{6}x_{7}$ or both. $X_{i}$ can take values from 0 to 9, but 2 followed by seven $0_{s}$ is not a valid account number. What is the maximum possible number of customers having a ‘magic’ account number?

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