Which of the following agreements is void?

Contract Act Section 20 will only apply when the following three conditions are fulfilled: •         The mistake must be committed by both the parties i.e must be mutual •         The mistake must be regarding some fact. •         It must relate to a fact which is essential to the contract. Therefore, if the mistake is made regarding the existence of the subject matter or a fact essential to the contract, it would be a void contract since there is no consensus ad idem. But an incorrect opinion regarding the value of the thing which forms the subject matter of the agreement is not said to be a mistake of fact and is considered inconsequential to the agreement.