Said sum of —— Dollars per day is hereby agreed upon, fixed and determined by the parties hereto as the liquidated damages which said Sanitary District will suffer by reason of such defaults, and not by way of a penalty. 10. Changes in Plans. The Board reserves the right to change the alignment, grade, form, length, dimensions or materials of the sewers or any of their appurtenances, whenever any condition or obstructions are met that render such changes desirable or necessary. In case the alterations thus ordered make the work less expensive to the Contractor a proper deduction shall be made from the contract prices and the Contractor shall have no claim on this account for damages or for anticipated profits on the work that may be dispensed with. In case such alterations make the work more expensive, a proper addition shall be made to the contract prices. Any deduction or addition as aforesaid shall be determined and fixed by the Engineer. 11. Extensions and Additions. In the event that any material alterations or additions are made as herein specified which in the opinion of the Engineer will require additional time for execution of all the work under this contract, then, in that case the time of completion of the work shall be extended by such a period or periods of time as may be fixed by said Engineer and his decision shall be final and binding upon both parties hereto, provided that in such case the Contractor, within four (4) days after being notified in writing of such alterations and additions, shall request in writing an extension of time, but the provisions of this paragraph shall not otherwise alter the provisions of this contract with reference to _liquidated damages_, and the said Contractor shall not be entitled to any damages or compensation from the said Sanitary District on account of such additional time required for the execution of the work.