Under FIDIC Red Book 1999, Sub-Clause 12.3 [Evaluation] governs how the Engineer determines the value of work done. Sub-Clause 12.3(a) sets out conditions under which existing rates and prices in the Contract should be used for valuation, even if the quantity of work changes. It includes criteria such as similarity of work, similar conditions, and that the rate is appropriate.

However, the statement in the question is incorrect because it implies that all four criteria must be satisfied simultaneously before a new rate can be applied. In reality, FIDIC does not require all criteria to be strictly fulfilled in a cumulative manner. Instead, the Engineer exercises professional judgment to determine whether existing rates are appropriate. If they are not appropriate—due to significant changes in quantity, conditions, or nature of work—then new rates or prices may be determined.

Furthermore, Sub-Clause 12.3 provides flexibility and refers to Clause 13 [Variations and Adjustments] where necessary. The valuation process is not rigidly conditional upon all criteria being met but rather guided by fairness and reasonableness.

Therefore, the statement is false because it misinterprets the application of the criteria as absolute and cumulative, whereas FIDIC allows discretion and does not impose such a strict requirement.