function _createCBOND(
  address liquidityToken,
  uint256 amount,
  uint256 syncMaximum,
  uint256 secondsInTerm,
  bool gradualDivs,
  address sender
) private returns (uint256) {
  require(
    tokenAccepted[liquidityToken],
    "liquidity token must be on the list of approved tokens"
  );

  //record current Sync supply and liquidity token supply for the day if needed
  recordSyncSupply();
  recordTokenSupply(liquidityToken);

  //determine amount of Sync required, given the amount of liquidity tokens specified, and transfer that amount from the user
  uint256 liquidityValue = priceChecker.liquidityValues(liquidityToken);
  uint256 syncValue = priceChecker.syncValue();
  //Since syncRequired is the exact amount of Sync that will be transferred from the user, integer division truncations propagating to other values derived from this one is the correct behavior.
  uint256 syncRequired = liquidityValue.mul(amount).div(syncValue);
  require(
    syncRequired >= syncMinimum,
    "input tokens too few, sync transferred must be above the minimum"
  );
  require(
    syncRequired <= syncMaximum,
    "price changed too much since transaction submitted"
  );
  require(syncRequired <= MAX_SYNC_GLOBAL, "CBOND amount too large");
  syncToken.transferFrom(sender, address(this), syncRequired);
  require(
    IERC20(liquidityToken).transferFrom(sender, address(this), amount),
    "transfer must succeed"
  );

  //burn sync tokens provided
  syncToken.burn(syncRequired);

  //get the token id of the new NFT
  uint256 tokenId = _getNextTokenId();

  //set all nft variables
  lAddrById[tokenId] = liquidityToken;
  syncPriceById[tokenId] = syncValue;
  syncAmountById[tokenId] = syncRequired;
  lTokenPriceById[tokenId] = liquidityValue;
  lTokenAmountById[tokenId] = amount;
  timestampById[tokenId] = block.timestamp;
  lastDivsCashoutById[tokenId] = block.timestamp;
  gradualDivsById[tokenId] = gradualDivs;
  termLengthById[tokenId] = secondsInTerm;

  //set the interest rate and final maturity withdraw amount
  setInterestRate(
    tokenId,
    syncRequired,
    liquidityToken,
    secondsInTerm,
    gradualDivs
  );

  //update global counters
  cbondsMaturingByDay[
    getDay(block.timestamp.add(secondsInTerm))
  ] = cbondsMaturingByDay[getDay(block.timestamp.add(secondsInTerm))].add(1);
  cbondsHeldByUser[sender][cbondsHeldByUserCursor[sender]] = tokenId;
  cbondsHeldByUserCursor[sender] = cbondsHeldByUserCursor[sender].add(1);
  totalCBONDS = totalCBONDS.add(1);
  totalSYNCLocked = totalSYNCLocked.add(syncRequired);
  totalLiquidityLockedByPair[liquidityToken] = totalLiquidityLockedByPair[
    liquidityToken
  ]
  .add(amount);

  //create NFT
  _safeMint(sender, tokenId);
  _incrementTokenId();

  //submit event
  emit Created(
    liquidityToken,
    syncRequired,
    amount,
    syncValue,
    liquidityValue,
    tokenId
  );
  return tokenId;
}