pragma solidity >=0.4.22 <0.7.0;

contract Payment {

    address payable public owner;
    uint public price;

    constructor(uint _price) public {
        require(_price > 0);

        owner = msg.sender;
        price = _price;
    }
    
    modifier onlySufficientResources() {
        require(msg.value >= price, "Not enough resources!");
        _;
    }

    //not recommended practice//
    function payService1() onlySufficientResources public payable {
        require(msg.value >= price);

        bool sent = owner.send(msg.value);
        require(sent, "Failed to send Ether");
    }
    
    //not recommended practice//
    function payService2() onlySufficientResources public payable {
        require(msg.value >= price);

        owner.transfer(msg.value);
    }
    
    //currently recommended practice//
    function payService3() onlySufficientResources public payable {
        require(msg.value >= price);

        (bool success,) = owner.call{value:msg.value}("");
        require(success, "Failed to send ETH");
    }
    
    function kill() public {
      require(msg.sender == owner);
      selfdestruct(msg.sender);
   }
}