Bank.sol

pragma solidity >=0.4.22 <0.7.0;

contract Bank {
    mapping(address => uint256) balance;
    address[] public customers;

    event Deposit(address customer, string message);
    event Withdrawal(address customer);

    function deposit(string memory message) public payable {
        require(msg.value > 10);
        balance[msg.sender] += msg.value - 10;

        customers.push(msg.sender);

        emit Deposit(msg.sender, message);
    }

    function withdraw() public {
        uint256 b = balance[msg.sender];
        balance[msg.sender] = 0;
        msg.sender.transfer(b);

        emit Withdrawal(msg.sender);
    }

    function getBalance() public view returns (uint256) {
        return balance[msg.sender];
    }
}