therefore had or had not been recorded as having been spent on the extra work. To the amount of labour and supervision agreed on may be added to the proper percentages of the amount paid for Workmen's Compensation, Vacation Pay, Unemployment Insurance and the Firm's Contribution to Pension Plan. Payment will be made on such itemized bills of cost to the contractor plus 15% of that bill. 

iii. Equipment rented by the Contractor will be paid at the invoice rate plus 15% unless the invoice rate exceeds the O.P.S.S. rate or when the invoice rate includes an operator exceeds the O.P.S.S. rate when the established rate of the operator is deducted. Equipment exceeding the