function newLottery() public {
        if (lotteryStart != 0) {
            require(block.timestamp >= (lotteryStart + 7 days), "lottery has not completed");
        }

        for (uint ticket = 0; ticket < ticketsAvailable; ticket++) {
            owner[ticket] = address(0);
        }

        ticketsAvailable = 100;
        ticketPrice = 10 finney;
        lotteryStart = block.timestamp;
    }