    function set_sale_open() public only_owner {
        require(db.get_presale_arbits_per_ether() > 0);
        require(db.get_arbits_max_contribution() > 0);
        require(db.get_arbits_min_contribution() > 0);
        require(db.get_pre_kyc_bonus_numerator() > 0);
        require(db.get_pre_kyc_bonus_denominator() > 0);
        db.set_arbits_presale_open(true);
    }