function sendTokens(uint256 _amount, uint256 _ethers) internal {
        keeppetToken.sendTokens(msg.sender, _amount);
        RefundVault refundVaultContract = RefundVault(refundVault);
        stat.currentFundraiser += _amount;
        stat.ethAmount += _ethers;
        stat.txCounter += 1;
        refundVaultContract.deposit.value(_ethers)(msg.sender);
    }