As regards payment for the additional work which the contractor was directed to do it was provided that: (i) The contractor shall be paid at the same rates as are specified in the tender for the main work; (ii) If the additional work included any class of work for which no rate was specified in the contract then the con tractor shall be paid at the rates entered into the schedule of rates of the C.P.W.D. Schedule of Rates 53 54 on which the estimated cost shown on page 1 of tender is based and if the tender for the original work is a percentage above the schedule rates the additional work shall be chargeable at the said schedule rates plus the same percentage deductions/addition; and (iii) If such class of work is not entered in the said Schedule of Rates then the contractor should inform the Engineer in charge within seven days of the receipt of the order the rate he wants to charge for such class of work and the Engineer in charge, if he does not agree to the said rate, may cancel the order for such additional work and if the contractor has commenced the work or incurred expendi ture in regard thereto before the determination of the rates the contractor shall be paid in respect of work carried out or expenditure incurred by him prior to the determination of the rates according to such rates or rates as shall be fixed by the Engineer in charge and in the event of a dispute the decision of the Superintending Engineer of the Circle would be final.