contract helloworld { uint total_funds; mapping(address => uint) funds; constructor(address owner) { total_funds = 90000; funds[owner] = total_funds; } function transfer(address from, address to, uint amount) public { funds[from] = funds[from] - amount; funds[to] = funds[to] + amount; } function balance(address owner) public view returns (uint) { return funds[owner]; } }