民用工程合同书(32)

　　　　（c）change the character or quality or kind of any such work;
　　　　（d）change the levels， lines， position and dimensiona of any part of the works;and
　　　　（e）execute additional work of any kind necessary for the completion of the works;
　　and no such variation shall in any way vitiate or invalidate the contract， but the value， if any， of all such variations shall be taken into account in ascertaining the amount of the contract price.
　　no such variations shall be made by the contractor without an order in writing of the employer. provided that no order in writing shall be required for increase or decrease in the quantity of any work where such increase or decrease is not the result of an order given under this clause， but is the result of the quanti - ties exceeding or being less than those stated in the bill of quan - tities.
　　all extra or additional work done or work omitted by order of the employer shall be valued at the rates and prices set out in the contract if， in the opinion of the employer， the same shall be applicable. if the contract does not contain any rates or prices applicable to the extra or additional work， then suitable rates or prices shall be agreed upon between the employer and the con- tractor. in the event of disagreement the employer shall fix such rates or prices as shall， in his opinion， be reasonable and proper.
29　adjustment of contract price due to variations in quantities.
　　should the total aggregate sum of all monthly progress payments excepting payment for additional work， provisional sumitems exceed or fall short of the original total contract price，then adjustment shall be made to the original total contract price upon completion of the work as follows;
　　　　（a）in case the total aggregate sum of all monthly payments is more than one hundred and twenty （120）percent of the original total contract price， then the amount exceeding one hundred and twenty （120） percent of the original total contract price shall be calculated and paid at eighty （80） percent of the amount