  function _computeEmissionRate() internal returns (SD59x18) {
    uint256 amount = source.liquidatableBalanceOf(tokenOut);
    // console2.log("_computeEmissionRate amount", amount);
    if (amount < minimumAuctionAmount) {
      // do not release funds if the minimum is not met
      amount = 0;
      // console2.log("AMOUNT IS ZERO");
    }
    return convert(int256(amount)).div(convert(int32(int(periodLength))));
  }
  function swapExactAmountOut(
    address _account,
    uint256 _amountOut,
    uint256 _amountInMax
  ) external returns (uint256) {
    _checkUpdateAuction();
    uint swapAmountIn = _computeExactAmountIn(_amountOut);
    if (swapAmountIn > _amountInMax) {
      revert SwapExceedsMax(_amountInMax, swapAmountIn);
    }
+    if (_emissionRate == 0) {
+      revert EmissionIsZero(_emissionRate);
+    }
    _amountInForPeriod += uint96(swapAmountIn);
    _amountOutForPeriod += uint96(_amountOut);
    _lastAuctionTime += uint48(uint256(convert(convert(int256(_amountOut)).div(_emissionRate))));
    source.liquidate(_account, tokenIn, swapAmountIn, tokenOut, _amountOut);
    return swapAmountIn;
  }
