function getFee(uint _base, uint _amount) external view returns (uint256 fee);
}




contract Ownable {
  address private _owner;
  address private _admin;

  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );

  event AdministrationTransferred(
    address indexed previousAdmin,
    address indexed newAdmin
  );


  
  constructor() public {
    _owner = msg.sender;
  }